India's Revised National Tuberculosis Control Programme (RNTCP), based on Directly Observed Treatment Short-Course (DOTS) strategy, began as a pilot project in 1993 and was launched as a national program in 1997. Three categories of treatment were recommended based on disease characteristics. Category III regimen comprised of thrice-weekly isoniazid, rifampicin and pyrazinamide in the intensive phase; with isoniazid and rifampicin in the continuation phase. This regimen was recommended for sputum smear negative and extrapulmonary tuberculosis (TB) patients who were not seriously ill. The omission of ethambutol in non-cavitary, smear-negative pulmonary TB patients who were known to be human immunodeficiency virus (HIV) negative was endorsed by the World Health Organization (WHO) guidelines. However, in view of high level of initial resistance to isoniazid in many areas, recent guidelines recommend adding ethambutol in the intensive phase, effectively eliminating category III.