Polymerase chain reaction (PCR) detection of mycobacteria from gastric aspirate for the diagnosis of tuberculosis is not fully evaluated up to now. A total of 116 gastric aspirate specimens were collected from patients with suspected pulmonary tuberculosis. The breakdown of diagnosis was 67 pulmonary tuberculosis, 16 nontuberculous mycobacterial infection, 5 extra pulmonary tuberculosis, and 28 other lung diseases. The conventional methods were shown to have a sensitivity of 47.8% and a specificity of 79.6%; on the other hand, Amplicor had 34.9% and 97.0%, respectively. The Amplicor provided a more rapid and specific method for diagnosing tuberculosis and was more useful than the conventional.