We are interested in determining the heritability of cryptorchidism (retained testicles) in the horse. If the testicle is retained it can be in the inguinal canal or intra-abdominal. The surgery to find the testicle can be straightforward but can be complicated by previous attempts, odd location of the testicle, smaller size, and lack or room to work. The surgery is more expensive than a castration. More information on the heritability of this condition would allow breeders and owners to make more informed decisions.