The Middlebrook-Dubos hemag-glutination, the phosphatide kaolin agglutination, and gel double diffusion tests were used as a battery of serologic procedures to detect 1 or more of the different antibodies that might be present in tuberculous sera. Using high limiting titers favoring specificity, 85% of bacteriologically positive patients were serologically positive to 1 or more of the tests. Only 6% of the tuberculin-negative controls were positive. Fifteen per cent of the bacteriologically positive patients were serologically negative.