In a retrospective survey of 145 patients coming to autopsy at a hospital in Sydney, 31 were found to have some form of renal papillary necrosis (RPN). Sixteen (52%) of those abused analgesic mixtures, there being a marked female preponderance (70%). A further two cases may have been linked with indomethacin and phenylbutazone. On the other hand, 15 (48%) of other analgesic abusers did not develop RPN and the differences between the two groups of abusers and a thrid group of non-abusers were studied in the hope of isolating a precipitating factor. Examination of concomitant drug intake revealed a positive correlation of RPN in abusers with the taking of diuretics and antihypertensive drugs. While these drugs may have been precribed to correct the sequelae of a silent renal lesion, an interactive component in its pathogenesis cannot be ruled out. Analgesic abuse but not RPN was linked with an increased consumption of barbiturates, psychotropic drugs, cardiac glycosides and antacids. Drug interactive effects may partly explain the sudden emergence of analgesic nephropathy 20 years ago.