The molluscicidal toxicity of abamectin against two economic snails namely, the brawn garden snail (Eobania vermiculata) and the white garden snail (Theba pisana), was established under in vivo conditions. Abamectin was used by the topical application technique. The mortality of snails was recorded after 24 and 72 hrs of exposure. The obtained results revealed that E. vermiculata was more resistant to abamectin than T. pisana. The LD50 for E. vermiculata after 24 and 72 hrs of exposure were 0.379 & 0.250 μg/ gm b.w, respectively. Whereas the LD50 for T. pisana were 0.199 and 0.125 μg/ gm b.w after 24 and 72 hrs of exposure, consecutively. On the other hand, the impact of abamectin upon GABA- Transaminase concentration was estimated in both snails. For the first time, the activity of GABA- T was estimated by HPLC. Abamectin has been assessed with 1/2, 1/5 and 1/10 of LD50 for 24 and 72 hrs of exposure. The most effective dose on GABA- T activity was 1/2 of LD50 after 24 and 72hrs of application for both snails.