The human immunodeficiency virus (HIV) epidemic is associated with increased incidence of tuberculosis. There is a need to provide prophylaxis for the same. Mycobacterium w, a non-pathogenic, atypical mycobacterium, shares antigenic determinants with Mycobacterium leprae and Mycobacterium tuberculosis. The tuberculin response, which is a delayed hypersensitivity reaction, indicates the status of cellular immunity against tuberculosis. The objective of this study was to evaluate potential of mycobacterium w for tuberculin conversion in HIV seropositives. Fifty HIV positives (tuberculin negative) were enrolled in this study and were administered intradermal mycobacterium w. In all the patients, Mantoux test was performed to determine tuberculin like delayed type hypersensitivity reaction, by measuring the area of erythema and induration at baseline and then after ninety days. The results of the study revealed that forty-eight out of fifty, had tuberculin conversion after ninety days.