Any dog can be aggressive. I was attacked by a Chihuahua when I was 10, and still have the scars on my shin. I have a AmStaff, and he is the most loving dog you could ever meet. What is so sad is that so many people are anti-Pitbull, AmStaff, and they really don't know about the dog. I suggest that you check this site out: http://www.cyberpresence.net/pb/pbweb.html. Really wonderful site. I am just glad that there are positive posts about this breed. They are extremely smart, very, very loyal and all they want is your love and approval. Rebel has stolen my heart, I can't imagine a better dog!!