The selection of biting sites by Anopheles albimanus on a human host was studied in the laboratory. The perception of exhaled breath guided the mosquitoes towards the head region, and was associated with a preference (P < 0.001) for biting this part of the body. Subsequent removal of breath resulted in a strong reduction of the number of bites on the head (from 49 to 20%). The significance of these findings in relation to host location is discussed.