Of 1,019 Chinese patients with radiologically active pulmonary tuberculosis but with sputum negative for acid-fast bacilli on 5 initial microscopic examinations who were studied for 5 yr, 364 (36%) had 1 or more initial sputum cultures positive for Mycobacterium tuberculosis. All 1,019 patients were randomly allocated to (1) selective chemotherapy (antituberculosis chemotherapy not being started until the disease had been confirmed to be active); or to (2) daily streptomycin, isoniazid, rifampin, and pyrazinamide for 2 months; or (3) for 3 months; or to (4) a standard 12-month control regimen. In the 364 patients with 1 or more of their initial sputum cultures positive, the short-course regimens were inadequate, being followed by relapse rates of 32 and 13%, respectively, during 60 months, compared with 5% in the control series. In the 655 patients with all their initial cultures negative, the corresponding relapse rates were 11, 7, and 2%. In the selective chemotherapy series, 57% of the patients had treatment started during the 60 months because their disease was confirmed to be active.