Canine cryptorchidism is a congenital defect that results from sex-limited autosomal recessive gene(s). Incidence is higher in some breeds, especially in smaller and inbred ones. Parents of affected puppies are carriers. Unilateral cryptorchid dogs can be fertile, and affected individuals and their siblings should be eliminated from a breeding program to decrease incidence of the defect. Androgen and gonadotropin treatments have been tried with little or no success. Bilateral orchidectomy is the treatment of choice because of the common sequelae of testicular neoplasia and torsion.