Large-scale validation of a simple latex agglutination test for the diagnosis of tuberculosis is described. Soluble antigens extracted from a non-pathogenic saprophytic mycobacterium, Mycobacterium w, which shares antigenic determinants with Mycobacterium tuberculosis, were covalently linked to carboxylated polystyrene latex beads. Batch to batch reproducibility of coated latex was ensured. Latex reagents were standardized to overcome non-specific agglutination. Reagents of the test are stable for 1 year at 4 degrees C. A total of 1,058 serum samples of pulmonary and extrapulmonary tuberculosis patients or patients with other pulmonary diseases and healthy controls living in endemic areas were tested. Sensitivity of 94% for pulmonary tuberculosis and 87% for extrapulmonary tuberculosis was obtained. Specificity is 92.2% for healthy controls and patients with other respiratory diseases. We conclude that the latex agglutination test can be utilized for mass screening for both pulmonary and extrapulmonary tuberculosis where diagnosis by existing methods is much more difficult.