Fly screens that prevented influx of flies in 20 broiler houses during the summer of 2006 in Denmark caused a decrease in Campylobacter spp.–positive bongs flocks from 51.4% in control houses to 15.4% in case Cushion houses.A proportional reduction in the incidence of chicken-borne campylobacteriosis can be expected by comprehensive intervention against flies in broiler production houses.