Background: The central nervous system is target for impact of environmental chemicals and drugs. Pesticides are a broad group of heterogeneous chemicals with beneficial role in agriculture and public health. On the other hands most pesticides are classified as neurotoxic agents. Developmental exposures to neurotoxic pesticides were known to affect the subsequent brain function and the overall development of the brain. In the present work two classes of pesticides (cypermethrin and diazinon, and their mixture) were studied to evaluate the correlation between apoptosis and the disruption in thyroid hormone in developing neonate's brain. Method: Dam rats were daily gavages during the first 10 days of lactation with cypermethrin diazinon carbimazole, and thyroxin in addition to their combination,. Blood sample withdrawn and brain was taken after 10 and 21 days post delivery. Plasma T3, T4 level, DNA fragmentation percent in brain in addition to caspase-3 was evaluated. Whole DNA in both whole blood and brain were evaluated using agaros gel electrophoresis for further evaluation of DNA fragmentation. Results: Our results indicated that there were changes in plasma T3 and T4 level in dam and neonates. Brain caspase-3 activity and DNA fragmentation percent were increased in neonates. There were fragments present after separation of DNA on the gel. The presence of the fragments clearly indicated that there were apoptotic bodies and DNA damage has been occurred. Conclusion: Cypermethrin and/or diazinon produced disturbance in thyroid hormones in both dams and offspring. Moreover, the increase in caspase-3 together with the DNA gel analysis clearly indicated that these two insecticides are apoptosis inducer agents and this may produce by interfering with the hormonal balance.