Two cases of alcaptonuria in siblings treated at a neurological hospital department for lumbar disc lesions with radicular symptoms are reported. Presence of ochronosis and characteristic radiological changes were demonstrated in the spine and iliac joints. The diagnosis was confirmed by biochemical investigations. The serum level of homogentisic acid was low (below 1 mg/100 ml) and its elimination with 24-hour urine was raised (1.27 to 1.89 g).