Forty-five ambulatory patients with primary fibromyalgia syndrome (PFS), 30 with rheumatoid arthritis, and 32 normal controls were administered 3 psychological tests: the Minnesota Multiphasic Personality Inventory (MMPI), the Life Events Inventory, and the Assertiveness-Aggressiveness Inventory. The PFS patients scored significantly higher on 8 MMPI scales when compared with the normal control group and on 4 MMPI scales when compared with the rheumatoid arthritis group. Further subgrouping of PFS patients according to MMPI scores showed that only 31% were "psychologically disturbed," 33% had a typical chronic pain profile, and 36% were within the normal range. The PFS patients scored higher than the rheumatoid arthritis and normal control groups on the Life Events Inventory but not the Assertiveness-Aggressiveness Inventory.