The effect of methomyl compound in vivo on three vital enzymes namely Glutamic Pyruvic Transaminase (GPT), Glutamic Oxaloacitic Transaminase (GOT) and Acetylcholinestrase (AchE) activities of succinea putrus , chocelicella acuta and Deroceras reticulatum tissues were investigated after 1,3 and 7 days of exposure under laboratory conditions. The results revealed that the biochemical response of (GPT) and (GOT) enzymes to methomyl compound were significant increase differences in activity during 1,3 and 7 days post-treatment for all the previous tested gastropods. Also, there were slight significant differences in (GPT) and (GOT) enzymes activities among either all treatments or time intervals. On the other hand, (AchE) activity was induced a significant decrease. Also, methomyl compound has inhibitory effect on this enzyme, the values were significantly for the first day of exposure till the end of the experimental period.