In the Hunter Valley, New South Wales, the incidence of renal pelvic carcinoma was found to be very high, and there appeared to be a causal relationship with analgesic abuse. The crude incidence rate was calculated at 1.6/100000 population per year. In half of the cases of renal pelvic carcinoma, there was evidence of analgesic abuse and/or analgesic nephropathy with papillary necrosis; in this group the male/female ratio was 1/2.6, and there was a tendency for the cancers to occur at a younger age. Tumours associated with analgesic nephropathy were more often poorly differentiated and in a more advanced stage at the time of diagnosis than those not associated with analgesic nephropathy. Multiple tumours were equally common in both groups, but coexistent flat carcinoma in situ tended to be more common in cases associated with analgesic nephropathy.