Cryptorchidism or retained testicles is one of the most common developmental defects in purebred dogs. The estimated frequency of this abnormality in several breeds is as high as 15 percent. Major health consequences of cryptorchidism are reduced fertility or infertility at adulthood, abdominal surgery to remove retained testicle, and if the dog is kept intact, significantly increased risk of testicular malignancies. According to the AKC rules, cryptorchid dogs have limited competitive opportunities, and such animals are not recommended for breeding. In certain individual dogs, a diagnosis is further complicated by later than average testicular descent, i.e some months after birth. Retained testicles in affected dogs should be removed to avoid the possibility of development of cancer. Currently, there is no genetic diagnostic test to predict the risk of the abnormality in a dog or the progeny. We will use an intensive candidate gene analysis and comparative gene mapping studies to search for genes associated with cryptorchidism in Siberian Huskies. We are working with the Siberian Husky Club to select affected and unaffected individuals from many families. Candidate gene(s) and genomic regions will either be identified as associated with cryptorchidism or excluded from further study. The ultimate goal is to develop a genetic test to remove carriers of this abnormality. All results will be published and available freely to all dog breeders.