The principal clinical features and radiological findings relating to the locomotor system have been studied in 32 consecutive hospital admissions of patients with Wilson's disease. 5 of these patients were recently diagnosed and had as yet received no treatment, while 27 were routine admissions for follow-up and biochemical supervision of their illness. No patient was specifically included or excluded from the series because of the presence or absence of locomotor symptoms. The most common radiological abnormality was a generalized increase of radiolucency, interpreted as skeletal demineralization (21 cases), followed by premature osteoarthrosis (8 cases). Changes in the spine were common and included osteochondritis, reduction of intervertebral joint spaces, osteoarthrosis, and a tendency to squaring of vertebral bodies. Other bony changes included fluffy irregularity of femoral trochanters, osteochondritis dissecans of the knees, osteophytic protrusions at bone ends, and bunches of tongue-like osteophytes at joint margins. The symptoms associated with these radiological abnormalities comprised back pain and stiffness with restricted movement, pain and stiffness of knees, hips, and wrists, and tenderness to pressure over margins of affected joints. Joint hypermobility was also observed in 9 patients. Episodes of acute polyarthritis with serological changes were seen in 5 cases; all these episodes appeared to be related directly to treatment with penicillamine.