A series of 63 patients (divided into 2 groups) with chronic polyresistant very extensive pulmonary tuberculosis often complicated by associated pathology were treated with Rifampicin (RMP) under supervision in a sanatorium. In group 1 (26 cases) RMP had to be used alone as the last therapeutic chance. At the end of the 1st and 2nd year the sputum was negative in 14 of 26 patients (55%) and in 10 of 20 patients (50%), respectively. Five patients died. In group 2 (37 cases, including 10 with associated pneumoconiosis) RMP could be and was combined with another drug; ethambutol (EMB) in most cases. The sputum was negative in 28 of 37 cases (75 %) after 6 months and in 14 of 22 cases (68 %) after 9 months. Only 1 patient died. As expected, the radiological results in both groups were poor because of extensive fibrosis accompanying oldstanding lesions and associated respiratory pathology including pneumoconiosis. Our findings contribute in an objective way to our notion as to what can be expected of RMP in the treatment of the type of case in question. It is stressed that better results could be obtained by the use of three-drug combinations consisting of RMP, EMB and another drug.