A comparative study of synovitis in Saudi Arabia and Malaysia was made with a view to determining any geographic variation in the incidence and pattern of the arthritides. The diagnostic spectrum in both series included pyogenic arthritis, rheumatoid arthritis, brucellar and tubercular arthritis, gout, pigmented villonodular synovitis, synovial chondromatosis and acute rheumatic fever. Date-palm thorn synovitis was observed only in the Saudi Arabian series. While brucellar and tuberculous arthritis were predominantly seen in Saudi Arabia, the incidence of rheumatoid arthritis, pigmented villonodular synovitis and acute suppurative arthritis was almost equal in both countries.