The molluscicidal activity of water extracts of pre- and post-harvested garlic (Allium sativum) was studied against the snailsLymnaea acuminataandIndoplanorbis exustus.The increase in 24-h toxicity of garlic bulbs from the 2nd to the 11th month after sowing, againstLymnaea acuminatawas 48.33 times, whereas againstI. exustusit was 24 times. The increase in toxicity of pre- and post- harvest garlic bulbs is discussed in relation to the synthesis of a chemical in the pre-harvested bulb and changes in the chemical composition of garlic after harvesting.