A total of 197 patients with pulmonary tuberculosis who had different haptoglobin phenotypes (Hp) were examined. Antituberculous agents were found to cause side effects in 145 patients during chemotherapy. In 82.7% of cases, adverse reactions occurred in patients with Hp 2-2 and Hp 1-1. Relapsing adverse reactions occurred mainly as allergic skin reaction and mixed syndrome. In 89% of cases, the pattern of relapsing adverse reactions did not coincide with the initial manifestations.