In order to determine the senstivity of the polymerase chain raaction (PCR) for rapid diagnosis of tuberculosis, 157 clinical specimens of sputum (n=111), urine (n=29), cerebrospinal fluid (n=6) and others (n=11) were examined with PCR and conventional method. Of these samples, 68 were obtained from tuberculosis patients (33 from smear and/or culture positive for Mycobacterium tuberculosis; 35 from patients with clinically active, smear and/ or culture negative), 29 from patients whose antituberculous treatment was interrupted one year previously, 59 from patients without any definitive diagnosis for tuberculosis and one from a patient whose sputum yielded atypcial mycobacterium. The PCR positivity for these groups was 76.4%, 24.1% and 25.4%, respectively. The polymerase chain reaction was negative in the sample from which atypical mycobacterium was isolated. The sensitivity of the PCR was found to be 100 % for the specimens with smear and/or culture positive for Mycobacterium tuberculosis complex (33/33). PCR was found positive in 39 (81.2%) of 48 sputum, 7 (87.5%) of 8 urine, 2 (67%) of 3 cerebrospinal fluid and 4 (44.4%) of 9 other specimens from active tuberculosis patients. These results indicate that the polymerase chain reaction can be used to detect Mycobacterium tuberculosis complex in urine and cerebrospinal fluid as reliably as in sputum.