A study to determine the prevalence of positive skin test reactions in an isolated region of southwestern Ethiopia where no previous surveys have been reported is described. Marked differences in the prevalence of positive skin tests between the population groups studied was found. The Dassanetch who live in large villages and have a high population density relative to other groups tested had the highest number of positives (53.7%). The Hamar who live in small scattered homesteads had the lowest number with 11.5%. The Bale, Suri, and Nyangatom who live in small to medium sized settlements had 32.5%, 27.9%, and 20.7% positivity respectively. Sex differences were minimal though men overall had a slightly higher rate than women (41.6% versus 38.9%). Age differences were marked, particularly where prevalence is high with the sharpest increase occurring under 14 years of age. A dispersed settlement pattern offers a distinct advantage in minimizing the incidence of tuberculosis for the populations of southwestern Ethiopia.