The author presents the results of studies and an analysis of experiments in the epidemiology and prophylaxis of tuberculosis which indicate careful observation of clinical cases. In each case the racial, social and economic conditions were analogous. Many controls were used. Dr. Saye has utilized the services of physicians in Chile, Argentina, Peru and Uruguay for the purpose of obtaining authentic local information. With the help of the data obtained from these investigators, he compares conditions in Montevideo with those in other countries in South America which have similar problems. The conclusions reached are conservative and indicate a rational scientific approach to the problems discussed.