The risk of developing renal papillary necrosis or cancer of the renal pelvis, ureter or bladder associated with consumption of either phenacetin or paracetamol was calculated from data acquired by questionnaire from 381 cases and 808 controls. The risk of renal papillary necrosis was increased nearly 20-fold by consumption of phenacetin, which also increased the risk for cancer of the renal pelvis and bladder but not for ureteric cancer. By contrast, we were unable to substantiate an increased risk from paracetamol consumption for renal papillary necrosis or any of these cancers although there was a suggestion of an association with cancer of the ureter.