The comparative efficacy of methomyl 20% SL and diazinon 60% EC insecticides used as baits or contact poison were studied against different ages of Eobania vermiculata. The LC₅₀ and LC₉₀ values of each compound were determine for the different ages(one, three, six, 9-12 months and over 24 months) of Eobania vermiculata.Serial concentrations of each compound were tested against land snail E. vermiculata using baiting and contact thin layer film (TLF) techniques. Mortality percentages were recorded after 24, 48 and 72 h., respectively. Methomyl was more toxic for E. vermiculata than diazinon, when used as poison bait at all different ages. Regarding the contact method, diazinon was more toxic to E. vermiculata at the three-month and (over 24 months) ages. Methomyl was more repellency to different ages of E. vermiculata than diazinon. The biochemical response of different ages (one, three, six, 9-12 month and over 24 months) of E. vermiculata treated with LC₅₀ of methomyl and diazinon compounds was also evaluated. Acetyl cholinesterase response of the three and six month's individuals differed with the rest ages to both compounds. The response of LDH and AST was obviously affected by the age of tested individuals and also application time. The effect of methomyl and diazinon on total protein and total lipids in the different ages fluctuated intervals of periods after treatment in different ages. Generally, it could be concluded that the response and susceptibility of tested snail to methomyl and diazinon differed according to different parameters i.e. chemical structure of pesticides, method of application, snail ages and time after treatment.