We evaluated the safety and efficacy of outpatient renal biopsy by prospectively comparing outpatient and inpatient renal biopsies in which patients were given the choice between having the procedure as an inpatient or an outpatient. Three hundred fifty renal biopsies were performed between January 1992 and August 1994; 118 patients had the procedure as an outpatient and 232 patients had the procedure with discharge planned for the following day. There was no difference between the two groups in terms of patient age, sex, or renal function. The complication rate for the two groups was not significantly different, with two inpatients having loin pain and one having macroscopic hematuria compared with one outpatient having loin pain and one having macroscopic hematuria. The biopsies provided samples of comparable size. We conclude that outpatient renal biopsy is a safe procedure and provides adequate tissue samples.