Renal insufficiency occurs in at least 1.5% of children with anaphylactoid purpura (AP). We reviewed the records of 16 children who developed end-stage renal disease (ESRD group) secondary to AP and matched them for age, era of onset, renal histology, and clinical severity at onset with 16 children who had AP but whose creatine clearance returned to and remained normal (recovery group). We reviewed creatinine clearances at 1, 3, 5, and 10 years after onset. A creatinine clearance greater than 70 ml/min per 1.73 m2 was present in 50% of the patients in the ESRD group at 3 years and in 25% at 5 years after onset. In contrast, all patients in the recovery group had a creatinine clearance greater than 70 ml/min per 1.73 m2 by 3 years (7 of 16 had a creatinine clearance greater than 125 ml/min per 1.73 m2) and all were normal 95-125 ml/min per 1.73 m2) by 5 years. Thus, the presence of an increased creatinine clearance (greater than 125 ml/min per 1.73 m2) at 3 years predicted recovery, while failure to reach a creatinine clearance of greater than 70 ml/min per 1.73 m2 at 3 years predicted progression to ESRD. There was no evidence of recurrent systemic AP or nephritis in the 14 patients who underwent renal allograft transplantation. We conclude that long-term evaluation of patients over many years is required to identify those who will progress to ESRD from AP and that recurrence of AP in the renal transplant is uncommon.