Mutations causing progressive retinal atrophy (PRA) are the predominant cause of hereditary blindness in the domestic dog. Although over a dozen PRA mutations have been identified, including prcd-PRA - which has been observed in over 25 breeds, many PRA mutations remain uncharacterized. During its nearly 15 years of operation, OptiGen has collected DNA, pedigrees, and detailed phenotype descriptions from hundreds of dogs that have been diagnosed with PRA by veterinary ophthalmologists. This PRA research sample set includes over 500 samples and 100 breeds. DNA testing of these samples has revealed that many breeds harbor multiple forms of PRA, often with similar clinical symptoms. Here we present the distribution of prcd and other PRA-causing mutations that have been assayed within OptiGen's PRA research sample set. Breeds in which multiple forms of PRA are known to segregate are presented as well as phenotypic variations in the PRA cases. Collaborative research projects that can make use of these samples are encouraged.