Nephrocalcinosis and nephrolithiasis developed in five children after furosemide therapy for congestive heart failure. In four children renal calcifications were detected by ultrasonography and in one by autopsy. Discontinuation of the loop diuretic in three children resulted in resolution of the calcifications in two of the patients. Residual renal morbidity included reduced creatinine clearance, microscopic hematuria, and hypercalciuria. The phenomenon of renal calcifications associated with furosemide treatment is more frequent than previously recognized.