Some laboratory experiments and field trials were conducted to study the effiecieney of acetic acid and the molluscicides methomyl against theterrestrial snails, Eobania. Vermiculata Müler and Monacha. obstructa Ferrosac were investigated under laboratory and field conditions. The results showed that, acetic acid had a highly significant effect on Monacha. obstructa than Eobania. vermiculata, whereas, the mortality percent was higher for M. obstructa (100%) at the concentration of 10% after 72 hrs. than E. vermiculata, which recorded (50%) mortality at the same concentration and the same time. The LC50 values recorded, 8.69 and 2.19% after 72 hrs of application for E. vermiculata and M. obstructa respectively. The effect of the applied compound (acetic acid) on certain biochemical parameters were recognized at the LC50 level, the total protein activities showed increasing for both snails species when compared with control .The same compound showed decrease in the level of total lipid from 4.96 to 2.78 for E. vermiculata while total lipid increased from 2.89 to 3.22 g/dl for M. obstructa respectively. Also decrease in the level of alkaline and acid phosphatase in both land snail species were recorded at Lc50 level .On the other hand, the results cleared that acetic acid achieved the decreased effect on the cholesterol for E. vermiculata while it increased the cholesterol for M. obstructa . On the other side, the obtained data of the field trials which carried out at Qalubyia Governorate Toukh district (shubra harris) in citrus orchards using acetic acid and methomyl proved that M. obstructa had more sensitivity to the tested compound than E. vermiculata.