The aim of the present study was to determine the acute toxicity of chlorpyrifos and deltamethrin in mice separately and to study their toxic and neurobehavioral effects. Median Lethal Doses (LD50
) of chlorpyrifos and deltamethrin were determined depending on up and down method. The oral LD50
of chlorpyrifos was 193.05 mg/kg and of deltamethrin was 15.71 mg/kg in mice. The oral administration of chlorpyrifos 155 mg/kg and deltamethrin 12.56 mg/kg represent 80% of LD50
resulted in acute signs of poisoning that manifested by dyspnea, salivation and lacrimation at 100%, piloerection, straub tail, tremors, convulsions and death at 70% for chlorpyrifos and 60% for deltamethrin and writhing reflex at 20% for chlorpyrifos. Oral administration of chlorpyrifos 310 mg/kg and deltamethrin 24 mg/kg increased severity of toxicosis signs as a percentage of piloerection, straub tail, tremors, seizures and death 100%. As well as decrease the onset of tremors, convulsions and death, writhing reflex which appears at 20% for chlorpyrifos and 10% for deltamethrin. After three hours of chlorpyrifos and deltamethrin oral administration at doses represent 20% and 10% of LD50
there are significantly hypoactivation in open-field activity, significantly increased in the duration of negative geotaxis performance, significantly decreased in head pocking and swimming scores compared to control group. In conclusion we found that deltamethrin was more toxic than chlorpyrifos this is based on the LD50
value. However, the signs of toxicosis and neurobehavioral effects produced by both toxicants were not differential and could not be associated with the toxic level.