Addition of antioxidant, sodium hypophosphite (SHP; 1 mM), to the diet of Zaprionus paravittiger (Diptera) results in depressed ATPase activity in both the sexes in comparison to the normal group. However, the rate of age-related decline in ATPase activity is lowered considerably in SHP fed group. Such changes in ATPase activity might be one of the important factors responsible for increased life span of flies with SHP feeding.