To estimate toxic actions of two insecticides on {lambda-cyhalothrin (Karilot gold 5%EC) and the biopesticide spinosad, (Conserve 0.24%CB)}, adults of the laboratory strain of Mediterranean fruit fly, Ceratitis capitata (Wied.) were treated with different concentrations. Discriminating value (LC₉₉) was selected for monitoring resistance in three field populations collected from different governorates (Qaluobia, Behira and Sharkia). Data showed that, males of laboratory strain as well as field colony strains were more susceptible than females. Qaluobia field colony exhibited the highest resistance level to lambda-cyhalothrin followed by Sharkia and Behira colonies in both male and female flies comparing with laboratory strain. Sharkia colony showed remarkable higher level of resistance to spinosad in males and females more than Behira and Qaluobia colonies. On the other hand, Ceratitis capitata flies of the different field strains showed remarked higher levels of the enzymes activity than the laboratory strain. Males showed the highest levels of acid phosphatase in Qaluobia, whereas Sharkia showed the highest level in females. The levels of alkaline phosphatase were higher in Qaluobia followed by Behira and Sharkia in both sexes. Behira had the highest enzymatic activity of AChE in male and female flies. The levels of total protein were higher in Behira than the other field colonies in males, but Sharkia exhibited the highest level in case of female flies. This means that the enzymatic activities play an important role in the insect resistance to spinosad and lambda-cyhalothrin, and there were positive correllation between resistance levels and enzymatic activity in the different field colonies.