Present trend in agricultural practice to control pest animals by using a mixed formulation of synthetic or natural pyretheroids with different proportions of organophosphates to reduce the toxic effect of organophosphate compounds toxicity on the human, domestic animals and environment. The mixed formulation selected for the present study neurella-D (chlorpyrifos 50% + cypermethrin 5%) was used for sub acute and acute toxicity studies. Based on the LD 50 values the sub acute doses were fixed [1/40th, 1/20th, 1/10th of the LD 50 Dosage]. The present work has been designed to asses the neuro toxicity of a combination pesticide through behavioral parameters [Psychopharmacological observation] and instrumental analysis such as spontaneous motor activity for 28 days. It is evident from the results that 1/20 and 1/10 of LD 50 dosed animals of either sex showed marked differences in the behavioral patterns when compare to 1/ 40 of LD 50 dose animals. When compare the neurotoxicity symptoms of constituent pesticide results show a different toxicological profile when compare with the toxicity of the combination pesticide whichmay be due to synergetic effect. Our study evident that the short time sub acute studies coupled with psychopharmacological evaluations can provide major part of the informationÂs obtained from the long-term studies.