Identification of snail species can be problematic on the basis of morphological and anatomical char-acters alone as some species show morphological plasticity and similarly morphological differentiationof cercariae found in snails may be difficult and this could lead to biased perceptions of intermediatehost spectra and transmission patterns. In this paper, we give an overview of the snail families and theirmedical and veterinary importance in Asia but with main focus on Vietnam.