Neutering reduces aggression against other animals. A male sensing a female in heat nearby may break down doors and jump fences, and will roam the neighborhood searching for her. Neutering relieves this sexual frustration and lets the dog relax and enjoy being a part of the family. Dogs have no psychological sex drive. They feel no need to reproduce, and are happier when they're neuterd.
Neutering is a relatively safe and painless operation done by a licensed veterinarian.
In some areas, neutered dogs are eligible for reduced license fees which soon make up the cost of the operation. By neutering your dog, you enhance its chances of living a long healthy life, save yourself a great deal of potential trouble and cost, and make your pet a more content family member.