The frequency of primary drug resistance in patients treated in hospital because of tuberculosis of the lung in 1983 was 2.3% (21 patients). Among them there were 5 patients (0.6%) with resistance to both INH and SM and 1 patient with a fourfold resistance. The frequency of secondary drug resistance was 20% (29 patients), among them a good third showed resistance to two or more drugs. Comparing to 1980 a decrease by half of patients treated repeatedly and also of the number of patients with secondary resistance can be recognized. Both the low share of primary drug resistance and the decrease of patients with repeated treatment indicate an effective therapy of tuberculosis in the GDR during the last years.