THE MINISTRY of Health of Vietnam has been surveying the 15 million people of that nation to detect cases of tuberculosis. Both the World Health Organization (WHO) and the U.S. Agency for International Development have provided assistance in this effort. At present, Mantoux tuberculin tests are administered, nonreactors receive bacille Calmette Guerin (BCG) vaccine, and positive reactors are given X-ray examinations. Persons with subsequently diagnosed tuberculosis are treated. The recent introduction of jet-injection equipment to the public heialth effort in Vietnam has made possible a new intradermal injection technique. Because of a shortage o,f medical and paramedical manpower, it was postulated that intradermal tuberculin skin testing by jet injection might expedite mass surveys through the more efficient utilization of exisiting personnel. To determine the effectiveness of testing for tuberculosis by jet injector as compared with the Mantoux technique, we used as a study population the 1,478 inmates of the National Mental Hospital, Bien Hoa, Vietnam. Inmates of the hospiital, who ranged in age from 8 years to over 70 years, were given tuberculin by both methods. Tuberculin skin testing had never been performed within the institution befo;re this trial, and the past medical history of the patients was generally unknown, although the hospital director felt that pulmonary tuberculosis was a major disease among his patients. History of BCG immunization preceding commitment to the hospital was not available. Our primary objective was to compare results of skin test readings after mechanical injection of tuberculin antigens,with those after use of needle and syringe (Mantoux method) on the same patient. If skin test readings after jet injection were disicovered to be equivalent to Mantoux test results, further investigations concerning speed of administration and survey campaign organization were to be undertaken.