The role of insecticides, profenofos, diazinon and thiamethoxam, was evaluated against Pegomya mixta infesting sugar beet plants at Kafr El-Sheikh Governorate during two successive seasons 1999/2000 and 2000/2001. The undesirable effect of these insecticides was estimated on certain associated predators, Coccinella undecimpunctata, Chrysoper‌la camas and Paedetus allierii. Diazinon demonstrates the highest toxic effect expressed as mor-tality percentage averages for the immature stages of P. mixta, after 15 days from treatment. The average of reduction percent was 80.9 % for the 1st and 81.3 % for the 2nd season, followed by profenofos (80.4 and 78 5 %). Thiamethoxam, however demonstrates the least averages (69.2 and 70.5 %). On the other hand, diazinon and profenofos demonstrate the highest toxic figures to the related predators, where the reduction aver-ages were 56.9 & 62.5 %, 64.9 & 63.9 % and 35.0 & 59.5 % for C. un-decimpunctata, Ch. camea and P. allied! for the 1st and 2nd seasons, re-spectively. Thiamethoxam ranks next in this respect. The average reduction percentages were 27.7, 31.0 and 25.6 % for C. undecimpunc‌tate, Ch. camea and P. allied!, respectively.