Autosomal-dominant polycystic kidney disease (AD-PKD) is the most prevalent inherited genetic disease of cats, particularly affecting Persians. Using archived tissue samples from 44 cats a genotype was successfully obtained by real-time PCR for 43 cats. Twenty-five cats (18 Persians, 4 domestic longhair cats and 3 domestic shorthair (DSH) cats) were found to carry the AD-PKD mutation and all of these cats had macroscopic and/or microscopic evidence of renal cysts consistent with PKD. Eighteen cats were found to be wild-type. Twelve of these (all Persians) had no pathological evidence of PKD, but the remaining 6 cats had evidence of renal cystic lesions. On pathological review the cystic lesions in 4 (2 Persians and 2 DSH) of these 6 cats were considered not to be consistent with a primary diagnosis of PKD. Histological evidence of polycystic kidneys was, however, confirmed in the remaining 2 cats (1 DSH and 1 Bengal) and may indicate that other PKD-causing mutations exist in the feline population.