The development of chemical attractants as baits for the house fly (Musca domestica L.) is described. A large number of compounds was first tested in an olfactometer. The materials which proved most attractive were tested in baited traps in a closed room. The best of these materials were then tested in the field in dry, open country, and in a humid area with rich vegetation. No single compound was so active that its attractiveness could not be enhanced by admixture. The most attractive material consisted of a combination, in aqueous solution, of malt extract 5%, ethyl alcohol 0.5% , skatole 0.02% and acetal 1%. For field use, 380 cc of this attractant solution was made into a paste with 240 g of fine-ground peat and 40 g of alfalfa meal.