Although diabetes mellitus is reported in 29% of patients with renal papillary necrosis (RPN), the frequency of RPN among patients with insulin-dependent diabetes mellitus (IDDM) has from autopsy studies been estimated to be only 4.4%. In vivo data on the prevalence of RPN in patients with IDDM have been lacking. We therefore studied the prevalence of RPN in 76 patients with long-standing IDDM and in 34 age-matched control subjects by intravenous urography. None of the control subjects showed radiographic signs of papillary necrosis. RPN was observed in 18 patients (23.7%); 15 were women (83.3%). Age and duration of diabetes was not different between patients with and without papillary necrosis, and there was no significant difference between the two groups regarding the prevalence of microangiopathic complications, i.e., proliferative retinopathy and diabetic nephropathy. Microscopic hematuria was three times more frequent in patients with than without RPN (44 vs. 16% P < .02). In addition, pyuria was reported in 40% of patients with papillary necrosis, and 61% of them gave a positive history of urinary tract infection compared to 16% (P < 05) and 32% (P < .02), respectively, in patients without papillary necrosis. It is concluded that RPN is a more frequent complication of long-standing IDDM than appreciated from autopsy studies, and being female and having a history of urinary tract infection are associated with an increased risk of RPN.