Congenital diaphragmatic hernia, affecting both sexes, was present in five of 27 puppies from three father-daughter matings. A purebred Golden Retriever was the common sire. The defect occurred in the left dorsolateral portion of the diaphragm, suggesting failure of closure of the left pleuroperitoneal canal during embryonic development. These findings, and a previous report of a similar defect in neonatal puppies, are consistent with autosomal recessive inheritance of canine diaphragmatic defects.