I'm starting to think he is more aggressive on his leash.. My Buddy brought over his dog lastnight..and they played, and chased each other for hours.. Neither dog was on the leash.. Wanted to make sure they would get along becuase his dog Toby is coming for some sleep overs.. I was worried because the aggression he was showing on the path with a leash.. He was the dog I got while ago and was off his leash.. But I will keep a eye on this matter..