The hypermobility syndrome has been recognized as a definitive diagnostic entity among children referred to a Pediatric Arthritis Clinic with musculoskeletal complaints. The diagnosis of hypermobility was made by the ability of the patients to perform at least three of the following maneuvers: (1) extension of the wrists and metacarpal phalanges so that the fingers are parallel to the dorsum of the forearm; (2) passive apposition of thumbs to the flexor aspect of the forearm; (3) hyperextension of elbows (greater than or equal to 10 degrees); (4) hyperextension of knees (greater than or equal to 10 degrees); (5) flexion of trunk with knees extended so palms rest on the floor. Of 262 patients, 15 (5.7%) referred to an arthritis clinic between January 1979 and July 1981 were subsequently determined to have hypermobility as the basis for their rheumatic complaints. Three of these 15 had concomitant juvenile arthritis. The presenting complaint of pain was most often localized to the knees, hands, and fingers. Arthritis and elevated ESRs were not seen except in the three patients who had concomitant juvenile arthritis. All patients responded to physical therapy and nonsteroidal analgesic anti-inflammatory drugs. This is an entity not sufficiently well recognized as a source of musculoskeletal complaints in the United States. It will usually respond well to reassurance and symptomatic therapy.