I think it depends on the dog (and the cat). Some dogs are very laid back and would have no problem accepting a cat no matter their age. Other dogs are very set in their ways and lack socialization making new introductions difficult. Some cats don't do well with dogs. I'd be particularly worried about a very old dog that has medical issues such as hearing or vision deficiencies, severe arthritis (or any other painful condition), etc. No matter the situation, if you decide to introduce a cat, do so gradually. If you are able, with your dog that has shown problems in the past, I'd expose him to some friend's cats for short supervised time periods and see how he reacts on several different occasions in different locations at home and away from home before jumping in and getting a permanent addition to your home.
at 12:22 AM on Oct. 10, 2010