Three anti-tuberculous regimens were compared in Algiers. The three regimens use Isoniazid and Rifampicin every day for six months; two of them used a third drug, Ethambutol or Pyrazinamide for the first three months. The results at 12 months after cessation of chemotherapy have already been reported. At 30 months (or 24 months after the end of treatment) the results were analysed for 513 cases: in 27 cases (5%) there was a relapse or therapy failed. Of 21 relapses 13 occurred in the first six months of follow up, four during the next six months, three during the third and one in the final six months. No further relapse was seen between the thirtieth and forty second months. All the cases of failure or relapse had received an additive chemotherapy. Two patients were on chemotherapy again for a relapse noted in under six months; the other 25 patients had a satisfactory outcome after receiving a regime of six to 12 months containing Rifampicin in 21 cases or a regime 12 months without Rifampicin in four cases. There was no statistically significant difference between the three therapeutic series for those cases with tubercle bacilli initially sensitive to the antituberculous drugs. On the other hand, for primary Isoniazid resistance a third drug is essential during the initial treatment. In the overall analysis pyrazinamide was as effective as Ethambutol in avoiding failure due to primary drug resistance and relapses up to 30 months.