A study was made of the radiological findings in 57 patients with a clinical diagnosis of analgesic nephropathy. The ages of the patients ranged from 27 to 72 years, and females predominated over males in the ratio 4·7 to 1. Renal failure varied from mild to very severe and the patients showed the usual high incidence of analgesic-induced gastro-intestinal, haematological and neurological disorders. In 82% of cases, kidneys were of normal size, but there was radiological evidence of reduced renal function in 85%. Thus, a small kidney with good renal function was unlikely to be due to analgesic nephropathy. Medullary necrosis was observed in 65%, and papillary atrophy and papillary necrosis each in 46%. Although usually gradual, acute massive sloughing of necrotic papillae could occur and occasionally led to ureteric obstruction. Papillary cavitation was seen in 39% but fistulae and ring shadows were observed in only 11% and 14% respectively, while renal calcification occurred in 26%. With the use of high dose techniques and retrograde pyelography, it is almost always possible to make a positive radiological diagnosis of analgesic nephropathy, even in patients with markedly reduced renal function.