A procedure is described for evaluating commercial residual pesticides commonly used for house fly control. Blotting paper panels were treated with candidate products and aged up to 5 weeks. During aging, these panels were tested thrice at 1, 3, and 5 weeks after their treatment for efficacy based on mortality of female house flies exposed to them for 24 h in a cage. A product is reported satisfactory if the average percentage kill obtained is not less than 80, 60, and 50 at 1, 3, and 5 weeks aging respectively or within 5 percentage points less than these limits. A product meeting first and third week mortality limits is also considered acceptable.