They are not aggressive in the sense that we normally see aggressive dogs that attack other dogs viciously. They are always dominant and will let any other breed know it. Once the other dogs stands down and becomes submissive it becomes all play! Now Cascorro our beloved male that has since passed on, which you see with my daughter on this web site, was very very mellow with all dogs unless they made the wrong move. But even after taking down some dogs in seconds flat, he would release without any harm to them and then lay down right next to them as if nothing ever happened. He was my wife's favorite, as he always attempted to sit on her lap! They are extraordinary animals like no others I have ever experienced before. They are very loyal and always want to please and seek your attention. I hope this enlightens you a bit more about this wonderful breed.