'T' lymphocyte population was estimated in 40 cases of various types of leprosy by E-rosette formation. The mean percentage value of T-lymphocyte was significantly low in lepromatous group as compared to tuberculoid and borderline leprosy. The mean percentage population of 'T' lymphocyte was also compared with 24 normal healthy control cases and significantly low levels were observed in all types of leprosy. The population of 'T' lymphocytes was also co-related with tuberculin tests in leprosy patients and healthy control cases. Lowest count of 'T; lymphocyte population and smallest diameter of erythema was observed in lepromatous leprosy, suggesting impaired cell mediated immunity in this group.