A differential diagnosis of polymyalgia rheumatica (PMR) and rheumatoid arthritis (RA) can be difficult in elderly patients, especially at the prodromal phase of RA. Furthermore, it was felt that there might be a diagnostic criteria for PMR specific to the Japanese. Accordingly, we have retrospectively studied the PMR patients who had come to our hospital, for making a diagnostic criteria. We especially stressed the distinguishing of PMR from RA in elderly patients. The criteria proposed are as follows: 1. Bilateral muscular pain persisting for 2 weeks at least in more than two of the following areas; neck, shoulders or shoulder girdle, upper arms, hips or pelvic girdle and thighs. 2. Normal serum myogenic enzymes. 3. ESR of more than 40 mm/h. 4. No swelling in the hand joints. PMR is defined by the presence of all of the 4 items. The criteria demonstrated a 93.1% sensitivity and 98.3% specificity for PMR.