Before adding a new dog to your household, the first thing to consider is whether you really want another dog just for the sake of having another dog. Although sometimes a new dog may work out to be a great companion to the dog you already have, there is really no way to know in advance if that will be the case. Dogs with separation anxiety frequently remain distressed even if there are other dogs in the house with them, and if the dogs turn out to be incompatible the new dog will introduce new problems.

Once you've decided to get another dog, you'll want to make the introduction with a minimum of stress. Here are some suggestions.

Give some thought to choosing a new dog who can be compatible with your present dog. In our experience, conflict is least likely to occur between a male dog and a female dog. Male with male is the next best combination, female with female is the combination most likely to result in conflict. When you choose a new dog, consider your present dog's needs. For example, try not to bring a very active young dog into a home with an older dog who already has health problems such as osteoarthritis. If you do get a puppy or young dog, be prepared to "protect" the older dog from her. You will have to spend plenty of time with the new dog and offer distractions to keep her from harassing the older dog.

• Try to introduce the new dog at a time when you will have at least a weekend to be home. You will want to observe and supervise closely at first. It is best not to leave two newly introduced dogs alone before they have become acquainted and the new dog is at least somewhat comfortable in his new home.
• Introduce the dogs in a neutral area rather than your own home or yard.
• Both dogs should be on leashes for control, but try to allow them a little room to maneuver. They may be calmer if they don't feel completely restrained. You will need one adult for each dog.
• Have the person walking the new dog approach from the side and "catch up" to you and your dog as you walk. Pick an area where you can walk together with a little distance between the dogs. As they walk they can look at and sniff each other, but there will be other things to catch their interest as well. Try to do this in an area without a lot of other people and dogs so that neither dog is over-stimulated. The walk should end at your home.
• If you have a yard and the weather permits, it may help to bring the dogs into the yard before going into the house. At first, allow them on a long leash until you notice relaxed and "wiggly" body postures and interest from both dogs. Once they appear relaxed and interested in a friendly manner, you can allow the leashes to drop so that they can interact.
• When you first enter the house don't let the dogs jostle each other in an entryway. Try to get both into the house quickly so that one doesn't react to the other's entrance later.
• Make sure there is an environment of plenty. There should be more than one water bowl and more than one comfortable place to lie down. There should be plenty of toys, especially of kinds your dog likes, so that there's no reason for the dogs to have a conflict over access to them. If your dog has a history of guarding his toys, they should be removed for the initial introduction period, which may take a few weeks. This all needs to be arranged before you pick up the new dog.
• At first, feed your dog the way you always have done and feed the new dog in a different room. Your dog should not have to worry about feeding time, leading to problems feeding the dogs. The new dog has no expectations of your home, so he shouldn't be upset by whatever feeding spot you choose. A very food-motivated dog will eat well from the start, but some dogs may need a person with them for the first day or two.
• Wait until you feel confident that the dogs are comfortable with each other before offering valuable treats such as real bones, rawhide, pigs' ears, etc., and supervise when you do. If your dog is reactive with these, you may have to separate the dogs before giving them these items. If your dog never gets these kinds of treats because he is aggressive over them, that should be the rule for the new dog too.
• Your dog may try to keep the new dog away from things that are very important to him. He may block the new dog from approaching you, from resting places like dog beds and furniture, or from rooms like the family room or the bedroom. If the new dog is very anxious, he may do the same, trying to keep your dog away from him in certain locations, or even sticking with a family member and trying to keep your dog away. Do not scold or punish the dogs if this happens. Instead, get up and move if it looks like you will be the center of contention, and distract either dog if he seems to be invading a place where the other is resting.
• Keep both dogs away from areas where food is being prepared or eaten at first. If either dog is anxious about the food, there could be a conflict.
• Don't change your dog's sleeping arrangements. If he sleeps in your bedroom, you'll have to decide whether the new dog will sleep there too. That may be the only way to avoid a lot of distress on the part of the new dog. He may have to be crated, though, at least in the beginning, to avoid problems during the night when you would be unprepared to intervene.
• Very few dogs coexist without disagreements. A stare, a lifted lip or a growl is a normal dog signal that he’s uncomfortable with something another dog is doing. Often the recipient of these signals will stop and move away—this is appropriate. There is likely to be some of this at first. As the dogs become more comfortable with each other they should do less of this, but punishing them can have very negative results. It can turn uncertainty into fear and aversion and result in ongoing conflict between the dogs.
• Supervise and distract as needed to make sure serious conflicts don't arise, but don't punish this sort of behavior. Examples of serious conflicts I include staring that cannot be interrupted, hard stiff muscles and posturing that lasts more than a few seconds, or full-contact fights. Please also monitor for excessive "bullying" behavior from one dogs towards another. If you notice that one dog is repeatedly avoiding eye contact and interactions, rolling over onto his back, or attempting to escape from the other dog. This can be an indication that one dog is uncomfortable and fearful and that the other dog is not appropriately responding to his avoidance cues.
• Don't leave the dogs together when they are alone in the house until you're reasonably sure that they are comfortable with each other. The new dog especially may be very anxious when left with your dog at first. If they can be crated, fine; if not, perhaps they can be gated apart. It may be difficult to separate them behind closed doors. Leave them for very short periods at first to make sure no problems arise when you're gone.
• Supervise play between the dogs at first. Dogs who are not well acquainted may do some rough play at first and this can result in growling or snapping. Be prepared to distract and redirect the dogs to another activity if play becomes too intense. As the dogs become more familiar with each other they usually learn to modulate their play.
• Any situation that raises the level of excitement in your environment should be avoided at first. The more time the dogs have to become acquainted before they have to deal with visitors or other disturbances the better. If you have children, do not let them or their friends interact with the two dogs without adult supervision.
• Remember that the new dog will have no idea at first how to signal that he needs to eliminate. Treat him as though you were beginning to housetrain him until he understands your routine. Try not to let him have accidents in the house; sometimes one dog will mark over the elimination of the other leading to housesoiling problems.
• As time goes on you'll learn more about the new dog's personality, but be careful at first of overwhelming him. People should not hug or kiss him, and there should be no rough play.
• Especially at first, avoid doing things to either dog that require restraint, such as grooming or bathing, in front of the other. A dog may attack the restrained dog if he is anxious about him.
• When using treats during daily activities, be sure there are plenty for each dog. You might start out with less attractive treats so as to avoid aggression over them.
• Be patient and keep in mind most dogs get along well once they are accustomed to each other.