Culex pipiens populations were collected in 5 localities of Grand Tunis area, Northeast Tunisia. Two samples (# 2, and 3) were susceptible to temephos insecticide. The resistant samples displayed RR₅₀ ranged from 1 for the sample # 2 to 213 for the sample # 5. The resistance level was high for sample # 5 (>100-fold), and low, not exceeding 3-fold in the other resistant samples.The temephos resistance could be explained by the AChE 1 insensivity and the increased detoxification by the CYP450. In the samples # 1, and 4 (temephos RR₅₀ <3-fold), the CYP450 were not involved in the temephos resistance and the insensitive AChE 1 could be the mechanism responsible for this resistance. The AChE 1 resistant phenotypes were present in the concerned samples with a frequency ranged from 0.18 to 0.46. For the sample which manifested high temephos resistance level (# 5), the insensitive AChE 1 seems play a role in the resistance, in addition to the major contribution of CYP450.