A metabolic disturbance in patients suffering from osteogenesis imperfecta is demonstrated. Abnormal aminoaciduria and low blood creatinine values were found in 6 such patients, belonging to 3 unrelated families. Low blood uric acid levels were found in 5 patients belonging to 2 of the 3 families. Among the clinically healthy relatives of the patients, abnormal aminoaciduria was found in 12 out of 17 persons examined. The blood creatinine levels, however, were normal. In 2 families blood uric acid values were low in 8 out of 13 persons.