We describe seven infants who developed renal calcification and bone demineralization following furosemide therapy with average daily doses of as little as 0.75 mg/kg per day. Renal calcifications were present in all seven cases and were more readily detected with ultrasonography than with plain films. Renal calculi were seen in four patients, sonographically demonstrated as echogenic foci in the dependent portion of the collecting system, usually accompanied by acoustic shadowing. One patient developed nephrocalcinosis, sonographically observed as echogenic medullary pyramids plus punctate, shadowing parenchymal calcifications. In two patients the location of the calcification could not be determined.