Rheumatoid arthritis is a chronic systemic autoimmune disorder causing inflammation of the synovial joints leading to joint destruction as well as a variety of extra articular features. In this present study, serum Adenosine deaminase and Alkaline phosphatase levels were studied in patients of rheumatoid arthritis. Thirty patients in the age group of 30-60 years of both sexes and equal number of age and sex matched healthy controls were included in this study. In rheumatoid arthritis patients, serum Adenosine deaminase levels were high, the mean serum Adenosine deaminase levels were 60 ± 9.55 and in controls the mean Adenosine deaminase levels were 21 ± 3.04. The p value was significant at p < 0.001. We conclude that serum Adenosine deaminase can be used as a marker for cell mediated immunity to monitor disease activity in rheumatoid arthritis. Serum Alkaline phosphatase was found to be raised in rheumatoid arthritis, the mean serum Alkaline phosphatase levels were 291.63 ± 35.84 in patients of rheumatoid arthritis when compared to healthy controls (196.73 ± 32.71).The p value was significant at p<0.001. The present study has focused on investigating the serum total Alkaline phosphatase levels in Rheumatoid Arthritis Patients and The findings have indicated a raised serum Alkaline phosphatase in patients of rheumatoid arthritis when compared to healthy controls thereby suggesting the role of serum Alkaline phosphatase as a marker of disease activity in rheumatoid arthritis. KEYWORDS: Rheumatoid arthritis, cell mediated immunity, Adenosine deaminase (ADA), Alkaline phosphatase (ALP). INTRODUCTION:Rheumatoid arthritis is the most common form of inflammatory arthritis affecting approximately 1-2 % of the world's population. (1) There is continuing interest in the metabolic changes occurring in rheumatoid arthritis. The etiology of rheumatoid arthritis is not known but it is classified as an autoimmune disease. (2) Immunological and inflammatory reactions play an important role in the initiation and perpetuation of rheumatoid arthritis.The autoimmune reaction in rheumatoid arthritis consists of activated Cd 4+ T cells. These T cells apparently function mainly by stimulating the joint to produce cytokines that are central mediators of synovial reaction which leads to joint destruction. These T cells have been shown to contain 5-20 times more activity of enzyme Adenosine deaminase than other lymphocytes.The physiological activity of ADA is related to lymphocytic proliferation and differentiation. The levels of ADA are elevated in diseases in which there is a cell mediated immune response as is seen in rheumatoid arthritis (3) therefore determination of serum ADA activity can be a useful indicator of increased lymphoreticular activities and can be used as a marker of cell mediated immunity in rheumatoid arthritis.