In cage tests of DDT residue treatments against houseflies {Musca domestica) it was found that on wooden surfaces 5% of DDT plus 5% of cyclohexanone in "Deobase" was slightly more effective than 5% of DDT in kerosene over a 207-day period with exposure limited to 1 and 5 min. On screen wire 10% of DDT in kerosene was more effective than the same conc. in butyl phthalate. On synthetic screen, a water suspension containing 5% of DDT, 5% of talc, and 2% of "Dreft" gave the best results, and on painted surfaces it was more effective than DDT in kerosene. Knockdown time was about the same with DDT in kerosene applied to plaster surfaces as with the same soln. applied to wooden surfaces. 1% DDT in calcimine gave 100% kill but slow knockdown. Strips of muslin treated with DDT and hung from the ceiling remained effective for 150 days. DDT dissolved in furniture polish and applied to mess hall tables gave good control, but under cage conditions was found to give poor results on newly lacquered surfaces.