1. A method has been described whereby the disability of hip disease, bilateral or unilateral, can be graded, and the quality of result following arthroplasty assessed, on a scale of numerical values. 2. The grade expresses the condition of the entire patient, rather than that of the hip joint alone. 3. Certain clinical criteria and physical tests have been adopted as the bases for scoring. The calculation of the patient's total score has been weighted to emphasise mobility, and to provide a more critical measure of the success of arthroplasty. Subjective tests (aside from the patient's estimate of his pain) are avoided, to provide as objective and accurate a method of assessment as possible.