One hundred and twenty cases of clinically diagnosed rheumatoid arthritis, 80 non-rheumatoid cases suffering from various other diseases and 40 healthy individuals were investigated for the presence of rheumatoid factor, quantitation of serum immunoglobulin, demonstration of ANA and LE cell phenomenon. Microlatex agglutination test of serum for rheumatoid factor showed 56.6% positivity in rheumatoid group and 3.7% positivity in non-rheumatoid group. All three serum immunoglobulins (IgG, IgM, IgA) were raised in serum in significant titre in cases of rheumatoid arthritis, whereas only IgA lever was elevated in the group of non-rheumatoid diseases. ANA and LE cell phenomenon were observed in 11.7% and 4.4% cases of rheumatoid arthritis who had severe underlying disease. In non-rheumatoid group, only one of 6 cases of systemic lupus erythematosus showed rheumatoid factor and that too in an insignificant titre (less than 1:20). Synovium and synovial fluid contained plenty of plasma cells and lymphocytes. It has been observed that RF appears first in synovial fluid and it may take several months to a year to attain detectable level in serum.