Despite Food and Drug Administration restrictions on its use above the ureterovesical junction, many investigators have used carefully monitored renal pelvic lavage with 10 per cent hemiacidrin for struvite calculi without serious side effects in hospitalized patients. We evaluated renal irrigations with hemiacidrin in 13 carefully selected patients (15 kidneys). In this high risk population (6 patients were paretic) initial treatment was done in the hospital but the remainder of 18 periods of extended renal perfusion (mean period 20 days) were performed at home. The total number of outpatient days of perfusion in this group was 365. All patients experienced external leakage around the perfusion catheter. Fever of greater than 101F occurred in 14 of 18 perfusions (78 per cent). Rehospitalization was necessary during 3 perfusions (17 per cent) and serum magnesium was elevated 3 times (17 per cent). Stones were dissolved successfully in 14 of 18 perfusions (78 per cent) but they recurred in 3 patients. No patient had altered post-perfusion serum creatinine levels. Outpatient perfusion of the renal pelvis with 10 per cent hemiacidrin under carefully controlled conditions appears to be a safe and cost-effective treatment for struvite or phosphate renal calculi.