A Strong breed predisposition to canine congenital adrenal hyperplasia-like syndrome (CAH-LS) exists and implies there is an hereditary cause. Pomeranians, one of the most predisposed breeds, have been reported to have partial adrenal dysfunction that could be associated with the pathogenesis of CAH-LS. In this study, the full-length complementary DNA (cDNA) of canine 21-OH, whose mutations are most likely responsible for the adrenal dysfunction in Pomeranians, was initially obtained from adrenal gland RNA by reverse transcription-polymerase chain reaction (RT-PCR), and its nucleotide sequence was determined. Genomic DNA samples from 16 Pomeranians and 30 control dogs, of seven different breeds, were tested for 21-OH gene polymorphisms by direct sequencing. No mutations affecting the primary structure and the transcriptional level of the 21-OH enzyme were found in Pomeranians. Our results indicate that the adrenal dysfunction in Pomeranians is not due to mutations of the 21-OH gene. This contrasts with the human form of CAH where 21-OH gene mutations are the major cause of the disease.