Numbers of fecal and vomit spots deposited by house flies, Musca domestica L., on spot cards were about twice as high on cards placed on the downwind sides as on the upwind sides of building support posts in caged-layer poultry houses with tunnel ventilation in Brooksville, FL. This trend was stronger at the ends of the houses where airflow is faster than in the relatively still-air center of the houses. A similar evaluation conducted in a pullet house (Zephyrhills, FL) with an evaporative cooling ventilation system revealed significantly higher fly counts on spot cards and sticky cards in downwind compared with upwind orientations. Flies in the pullet house were concentrated in both ends of the house and in the center, with comparatively fewer flies in the intermediate regions. There was a high degree of correlation between spot card and sticky card counts in the pullet house.