Tuberculosis Research Committee, RYOKEN, had carried out a clinical trial as to the therapeutic effects of RFP on retreatment cases of pulmonary tuberculosis from June, 1969, and the patients of this trial were followed up at three years interval after the beginning of the trial. At the start of the trial, all patients were divided into two groups. Patients of the group I had been treated previously by various antituberculosis drugs including EB, and RFP was administered daily together with the

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... previous regimen. The patients of this group might be classified as so-called monotherapy of RFP. Patients of the group II had never been treated with EB previously, and they were divided into two subgroups A and B at random. The patients of subgroup A (group II A) were treated with RFP daily plus EB daily, and the patients of subgroup B (group II B) were treated with RFP twice weekly plus EB daily. The dose of RFP in these three groups was equally 450 mg per day, and that of EB were 750 mg per day. The patients of each group were followed up at an intervall of three years from the beginning of this study and about ninety per cent of the cases were fully observed ; that is, 100 cases of the group I, 61 cases of the group IT A and 60 of the group II B could be followed up. Among these cases there were no significant differences in the background factors between II A and II B. The number of cases in each group which showed consecutively negative cultures at 4th, 5 th and 6 th month after the start of the trial were 47 (47%) in the group I, 44 (72. 1%) in the group II A and 48 (80%) in the group II B. There were some cases (1 case in group I, 6 cases in group II A and 3 cases in group II B) which showed negative conversion during 7-12 months. Including these cases, a total of 48 cases in the group I, 50 cases in the group