In the United States, spaying and neutering of dogs and cats is commonly performed to prevent the birth of unwanted pets. However, surgically removing the ovaries or testes may have unexpected consequences. Dogs that have been spayed or neutered have an increased risk for developing obesity, urinary incontinence, hypothyroidism, hyperadrenocorticism, diabetes, cruciate ligament tears, hip dysplasia, and cancer. Lymphoma is three to four times more common in spayed and neutered dogs compared to dogs left intact. In addition, dogs that are neutered before one year of age are three times more likely to develop lymphoma than dogs neutered after one year of age. This funded study is investigating the hormonal and cellular relationships between spaying/neutering and the development of lymphoma so that in the future new treatments will be available to extend life expectancies of dogs with cancer.