Of 1,033 Chinese patients with radiologically active pulmonary tuberculosis but with sputum negative for acid-fast bacilli on 5 initial microscopic examinations, 370 (36%) had 1 or more initial sputum cultures that yielded tubercle bacilli. All patients were randomly allocated to (1) selective chemotherapy, antituberculosis chemotherapy not being started until active disease had been confirmed, or to (2) daily streptomycin, isoniazid, rifampin, and pyrazinamide for 2 months or (3) the same 4 drugs daily for 3 months, or toi (4) a 12-month control regimen. In patients with 1 or more of their initial sputum cultures positive, the short-course regimens were inadequate, being followed by bacteriologic relapse rates of 15 and 9%, respectively, during 30 months, compared with 0% in the control series. In patients with all their initial cultures negative, the corresponding relapse rates were 4, 2, and 0%, and in the selective chemotherapy series, 53% of the patients had treatment started during the 30 months because active disease was confirmed (bacteriologically in 40%). It is important to continue studying short-course chemotherapy for smear-negative patients because in many countries they represent a high proportion of those treated.