A tsetse survey was conducted around the Lambwe Valley in South West Kenya in order to establish the extent of Glossina pallidipes distribution outside the Valley. Between October 1988 and March 1989 flies were found far outside the Lambwe Valley. A proportion of these flies was infected with three species of trypanosomes. The capture of teneral flies suggested that breeding was occurring and that viable populations of G. pallidipes therefore exist away from the core breeding areas in the valley.