Deer flies have been implicated as mechanical veotors of tularemia in Utah. Although infected flies heretofore have not been tound in nature, there is little doubt of their importance in transmitting tularemia to man. Two species present in this area, Chrysops discalis Williston and Chrysops noctifer Osten Sacken, have been shown experimentally to transmit the disease. The presence of deer flies in the environs of Utah Lake where tularemia is endemic oftera a potential health threat to man, and the expanding human population and development ot recreational facilities adjacent to the lake inorease this potential. Despite the taot that deer flies have been implicated with tularemia in Utah, little is known about their distribution or seasonal occurrence in the environs of Utah Lake.