Twenty-nine canine DNA samples, including samples from 11 members of an autosomal recessive retinal degeneration pedigree, were fingerprinted with a (CAC)n probe using a chemiluminescent method. Sixteen polymorphic bands were identified in the two pedigrees. Nine polymorphic bands were scored in one pedigree; seven polymorphic bands were scored in the other pedigree. None were sex-linked. Hybridization of the (CAC)n probe to total and poly A+ RNAs from different canine tissues revealed a prominent polyadenylated message at 6 kb that was present in the retina, spleen, and kidney but not in the liver or heart.