The designed experiments were carried to calculate the economic threshold levels (Ells) and economic injury levels (EILs) for the more existed land snail species Monadic cartusiana (Mullar) in wheat, dover, pea and lettuce fields at Sharkia governorate throughout winter season of 2006/2007. The gained results proved that the economic threshold and injury levels were vaned significantly for different tested crops. The relatively highest economic threshold level of 3.123 snail/plant was recorded on lettuce plants followed by 3.58 snail/100 plants of pea, while in case of clover and wheat crops were 3.193 and 3.224 snail/ m², respectively. As economic injury levels, the values were raised than that of ETLs recording the highest level of 37.478 snail/plant of lettuce followed by 17.00 snail/m² on dover plant and 12.00 snail/100 plant of pea while on wheat the EIL was 4.38/m2. Therefore, it could be concluded that the lettuce plants were more tolerant to land snails infestation than other tested plants, while pea plants were the susceptible ones.