Six to nine months is the traditional age before neutering is acceptable, although eight weeks is sufficient if the puppy is in good health. Neutering older dogs carries a risk of medical complications if the animal is overweight.
Besides the benefit of preventing unwanted pregnancies in domestic dogs, neutering reduces the risks of prostate-related maladies and testicular cancer. In addition, certain hormone-related behaviors are reduced if the animal is neutered. These include urine marking, roaming, aggression, mounting and social problems with other dogs. It is best to neuter a dog at the recommended age; otherwise, it is possible the animal will maintain some of these behaviors if it is old enough to have displayed them.