This review focuses on biologically active entities from invertebrate sources, especially snails. The reader will encounter several categories of compounds from snails including glycosaminoglycans, peptides, proteins (glycoproteins), and enzymes which possess diverse biological activities. Among glycosaminoglycans, acharan sulfate which was isolated from a giant African snail Acahtina fulica is reviewed extensively. Conotoxins which are also called conopeptides are unique peptide mixtures from marine cone snail. Conotoxins are secreted to capture its prey, and currently have the potential to be highly effective drug candidates. One of the conotoxins is now in the market as a pain killer. Proteins as well as glycoproteins in the snail are known to be involved in the host defense process from an attack of diverse pathogens. Carbohydrate-degrading enzymes characterized and purified in snails are introduced to give an insight into the applicability in glycobiology research such as synthesis and structure characterization of glycoconjugates. It seems that simple snails produce very complicated biological compounds which could be an invaluable source in future therapeutics as well as research areas in natural medicine.