In the early twentieth century, while smallpox, cholera, and other diseases caused temporary but urgent health crises in China, pulmonary tuberculosis remained a leading cause of mortality. This article investigates efforts to prevent and control tuberculosis in Republican China, especially efforts to implement the Bacille Calmette-Guérin (BCG) vaccine as a preventive measure against the disease. Published materials show that efforts to introduce this vaccine during the early 1930s met with skepticism on the part of Chinese physicians and inaction on the part of the state. Although the outbreak of the Second Sino-Japanese War (1937–1945) presented an obstacle to BCG research and development, it also provided new opportunities for members of China's biomedical research community—many of whom had moved with the Nationalist government to the nation's western hinterlands—to learn about new methods of producing vaccines and study methods of epidemic control. In the case of BCG, these processes bore fruit only in the years after the war ended, when a review of medical literature suggests that in the tumultuous years of civil war between 1945 and 1949, health administrators began to plan for implementation of the BCG vaccine on a large scale for the first time. But questions of the ability of this biochemical method to prevent an airborne disease, and the role of environmental and social factors in causing tuberculosis, lingered throughout this period.