Takahashi reported in 1962 that his kaolin-agglutination test (KAT), using the phosphatide fraction of Mycobacterium tuberculosis as antigen, was capable of detecting specific antibodies in sera from patients with pulmonary tuberculosis, and that the test could differentiate between active and inactive disease.The present study was designed to investigate the diagnostic efficiency of the KAT under conditions that prevail in Africa. Blood specimens were obtained from various categories of people, ranging from presumably healthy tuberculin-negative persons to patients with far-advanced pulmonary tuberculosis, and these specimens were submitted "blindly" for serological testing.The results showed that the KAT was less sensitive and also less specific in Kenya than it had been found in Japan by Takahashi. Some reasons for this discrepancy are discussed, but no final conclusion is reached.