The measurement of Rheumatoid Factor (RF) has been a valuable tool in diagnosing Rheumatoid Arthritis (RA) for many years. Since Waaler's discovery of the RF, many studies have been carried out. In the recent years studies have been shown that there is no such correlation between the level of the RF titers and disease activity. In this report we have measured the IgM-RF, IgA-RF and IgG-RF by an Enzyme linked immunosorbent assay (ELISA) for 144 normal human sera and 50 patients sera. At the same time we have measured the titers of gelatin particle agglutination (RAPA) and the Latex agglutination (RA-test). The value of IgG-RF have been most correlated to the titers of RAPA (r=0.9037). Using this ELISA technic to detect IgM-, IgA- and IgG-RF, have been aviable more clearly the activity and the stage of Rheumatoid disease.