I put my biggest on a leash - I don't even remember why we first put it on him, but he didn't seem to mind it, and since he always pesters us to go outside, we started taking him for walks. He was already grown - about a year old - when we first did this. We live on a street that is nothing but duplexes and fourplexes, with a few buildings from an aparment complex at the end. Behind our row of buildings is a wide grassy area, about 200 feet wide, I'd guess, that runs the length of the street. This is between the buildings and a creek that also runs the length. We all use this area as a park, walking dogs, throwing frisbees, etc. This is where we walk Big, so it is nowhere near the street. He just runs up and down, like a dog! Sometimes he'll try to get in the creek or up a tree, but we stop him. Since he weighs about 20 lbs, he has outgrown all my pet taxis, and he's too heavy to try to carry by nothing but a thin plastic handle, so his last two vet visits I took him on his leash. You should see all the raised eyebrows when we waltz into that waiting room! Biggie gets alot of attention, anyway, because he's so big, but he's the center of attention at the vet when he's on his leash! If he were a nervous cat, this probably wouldn't work, but he's so easygoing and docile, even with a waiting room full of dogs, that it has worked out really well so far.

By the way, we had two Siamese girls when I was growing up. Since my dad was an Air Force pilot, we moved frequently and needed a good way to manage the cats while traveling. We tried harnesses - once. 'Nuff said!