There are both medical and behavioral reasons to have your dog or cat surgically spayed or neutered. Spayed and neutered pets are less apt to roam, decreasing risk of fights or traumas such as being hit by a vehicle. Cats that are spayed and neutered are less prone to urine marking behavior.
Spaying a female dog or cat decreases the risk of breast cancer, especially if done before the first heat cycle. Other health benefits of spaying include avoiding uterine cancer and preventing the life-threatening uterine infection called pyometra.
Neutering male dogs has the benefits of eliminating testicular cancer, reducing prostatic disease, decreasing aggression, as well as decreasing behavior problems such as urine marking and roaming.