It depends on what/why we're needing vet visits. Once we had an outbreak of ear-mites. The vet suggested he making a house call since we have so many and this is something that all need to be treated at the same time or you don't get rid of them. Well it turned into a disaster and didn't go as planned. The cats were spooked to no end with the vet and tech in the house and Kevin got clawed to death trying to capture some of them. So we ended up taking 4 to 5 at a time making trips back and forth. What a nightmare. We learned that for the most part when the cats are at the vets in an unfamiliar environment they tend to get more submissive. So with all that said we try and limit to 2 at a time.