This work was carried out in the Institute of Medical Insect Research, Dokki-Giza-Egypt to study the toxic and some biochemical effects of chlorpyrifos-methyl and diflubenzuron on the mosquito Culex pipiens (L.), larvae and adults. Larvae sampled from ponds of 10^th of Ramadan and drainages of both Abo-Kbeer and Dyarb-Negm districts and adults from the adjacent houses of the same three regions, at Sharkia Governorate. Toxic effect on the larvae, the obtained results showed that the mortality percentages for chlorpyrifos-methyl and diflubenzuron were ranged between 32. & 96 and 47 & 86% at tenth of  Ramadan; at Abo-Kbeer, 32.5 & 98.75% and 32 & 96% and 38 & 92 and 53 & 94% at Dyarb-Negm; respectively. The LC₅₀ values were ranged between 0.0008 & 0.002 ppm and 0.2153 & 0.4084 ppm, respectively. Chlorpyrifos-methyl insecticide was more efficient than the diflubenzuron inhibitor in control larvae of Culex pipiens. Biochemical effects, on the two stages larvae and adult, chlorpyrifos-methyl insecticide affected on activity of β –esterase and α–esterase enzymes values with significant increase in  both the two districts 10^th Ramadan and Abo-kbeer and ranged between 10.77 except β–esterase activity was decreased in Abo-Kbeer by -1.29  In Dyarb-Negm drainage, the two enzymes cleared insignificant differences compared to control. Total soluble protein cleared significant decrease, whereas, in total lipid and AChE values were insignificant differences between treatments and control. Diflubenzuron insecticide affected on activity of  β–esterase values recorded significant increase in Dyarb-Negm for adult stage and insignificant values in the others districts whether for larvae or adult. α –esterase values in Abo-kbeer and Dyarb-Negm recorded significant increase with range between -6.01 and -33.11for the two stages and insignificant values in 10^th of Ramadan. Total soluble protein, lipid and AChE values recorded significant decrease for the two stages, except AChE values recorded significant increase in 10^th Ramadan compared to control. Chlorpyrifos-methyl and diflubenzuron play an important role in the toxic effect on the larval and adult stages of Culex pipiens as well as the biochemical components, which are positively reflected on their role in the control of the two stages. Chlorpyrifos-methyl insecticide was the best in toxicity, whereas, diflubenzuron was the best in effect on the biochemical components.