I only take small dogs, so I have had up to five dogs (including mine) at a time with no problems. I do introductions very slowly with high supervision and direction, encouraging them to play nicely, and it usually works out great. Only once did it not work out, but then I just used baby gates to keep two groups separated from each other and managed that carefully. We have a separate fenced front yard and back yard, so we have a pretty good set up for separating dogs if we need to. I never leave dogs alone together, period. If I have to shower or leave the house for any time, I crate everybody. Also, since they are small, I can walk them all at once, or in two groups if they aren't friendly. It really depends on the situation. I actually don't introduce my dog to the visitors at the meet and greet, because I know that she will act badly at first, but she always comes around and accepts the dogs with a bit of time. When a new Rover guest comes to the house, I crate my dog and all other visitors for at least the first hour, then slowly start trying introductions. If it doesn't work at first, I try again in a few hours, or even the next day. It seems to always work out if I am careful and patient, and give the dogs direction, praise, and treats for being nice to each other. I do have to be right there though, no walking away to do other things, a fight can break out very quickly if you stop paying attention to their body language, so it's more work with more dogs (of course). Be right there if you start hearing any snarling, give everybody a break, try again later. Anyway, that's what works for me, and it's been great so far.