250 patients suffering from pulmonary tuberculosis who were smear positive received a chemotherapy regime for 6 months combining Rifampicin and Isoniazid every day with a daily supplement of Pyrazinamide for the first 8 weeks. The three drugs given in the initial phase of treatment were administered either separately or in combined preparations according to the 2 controlled randomised groups. During the maintenance phase the drugs were given in a combined form in fixed proportions in the 2 groups. 6 months after the end of treatment the bacteriological results were similar in the 2 groups in the 144 cases which were analysed. Amongst 137 cases with bacilli which were initially sensitive to Isoniazid (68 cases with separate medicines at the beginning and 69 with combined drugs) there was no failure at 6 months, nor any relapse during the course of the first period of surveillance. Amongst 7 cases with bacilli which were originally resistant to Isoniazid (4 and 3 respectively), there were 2 failures at 6 months one in each group with acquired resistance to Rifampicin observed at the time of the failure. There was no difference in the therapeutic results observed whatever the presentation of drugs used during the initial phase of treatment.