Five mycobacterial antigens were compared in an enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of tuberculosis. The antigens studied were an unheated sterile culture filtrate of Mycobacterium tuberculosis, tuberculin purified protein derivative (PPD) from M. tuberculosis (PPDa), purified cytoplasmic protein antigens 5 and 6 from M. tuberculosis, and a PPD prepared from M. kansasi (PPDk). Multivariate analysis of variance showed that geometric mean titres obtained with each of the antigens in ELISA were significantly different in tuberculosis patients and in control groups. The covariation of the ELISA results with the five antigens was highly interdependent. Analysis of receiver operating characteristics revealed that the most accurate test was obtained with antigen 5. M. tuberculosis PPD, M. tuberculosis antigen 6, and M. tuberculosis culture filtrate were, in descending order, less accurate.