The incidence of post transplant tuberculosis is 15% in the developing world. The aim of this study was to evaluate effect of Isoniazid (INH) chemoprophylaxis on post transplant TB infection. Three hundred and sixty patients were randomized and 173 received INH prophylaxis at 300mg/day for one year and 187 without prophylaxis were taken as controls prior to transplantation. Primary disease and co-morbidities were similar in both groups. Immunosuppression was by triple drug. All patients were followed for 1 year. The exposure risk factors in treated group A and controls group B were, past TB 2.9% A vs 3.2% B, TB in close contacts 2.9% A vs 3.2% B, acute rejection 4.6% A vs 4.3% B, smoking 12.7% A vs 9.6% B. At one year follow-up 1 (0.57%) patient from group A and 9 (4.8%) from group B developed TB. Site of TB was pulmonary in 8, joint in 1 and lymph node in 1. The average duration of TB development was 32 weeks (range 11 – 64). The study has shown that INH prophylaxis reduces post transplant tuberculosis. Chemoprophylaxis may thus play an important role especially in developing centres where TB is endemic.