In a prospective survey, one hundred and eleven dogs with canine chronic renal disease, presenting to 24 veterinary practices in East Anglia and the West Midlands (geographical area 8,600 square miles) were identified. More than 20 different breeds were represented. In 76 cases, clinical details, blood and urine biochemistry, serology and kidney tissue for light and electron microscopy, and immunohistochemistry were obtained. Forty (52%) had glomerular (GN) and 36 (48%) non-glomerular (NGN) disease. Types of GN identified were (W.H.O. classification, number of cases in brackets): focal glomerulonephritis (gn) (5), diffuse mesangial proliferative gn (8), diffuse endocapillary proliferative gn (2), mesangiocapillary gn type I (8), diffuse crescentic gn (1), diffuse sclerosing gn (7), amyloid (6), unclassifiable gn (3). Eight dogs with GN and 13 with NGN had extra-renal lesions. In only one GN case (bacterial endocarditis) was the etiology clear. Proteinuria, but not age, breed, sex, serum creatinine or hematuria, discriminated between GN and NGN groups. This prospective survey identifies GN, with morphological types as found in humans, as a common cause of canine chronic renal disease.