Aims: To evaluate the effects of this insecticide on the embryonic development of kidney and to assess the important role of Notch2–Jagged1 pathway in this duration. Methods and results: Chlorpyrifos (CPF) 5 mg/kg/d were administrated on gestation 7.5–11.5 day by subcutaneous injection. On gestation 16.5 day, the normal embryo kidney developed through S shape duration to the original kidney, which had the nephrons and could start to secret the urine. But for the CPF-treated mice, the embryo kidney developed much more slowly, they did not show the S shape and the nephrons. The Notch2–Jagged1 pathway should be expressed stronger in the normal embryo kidney on gestation 16.5 day, but for the CPF-treated mice we found the obvious weak pathway staining. Conclusions: CPF broke the Notch2–Jagged1 pathway during the embryo kidney development, and the Notch2–Jagged1 pathway plays an important role in the S shape to original kidney formation duration. Birth Defects Res (Part B) 92:97–101, 2011. © 2011 Wiley-Liss, Inc.