With about 130000 species in 7 classes, Mollusca is the second largest animal phylum. Four mollusc classes are known from Ukraine: gastropods and bivalves are the most abundant and diverse, being represented by 450 and 200 species respectively; loricates (chitons) and scaphopods are represented by 1 to 3 species. The figures are approximate because of considerable differences in opinion about the status of many species and forms. Using traditional classifications, there are 73 Ukrainian freshwater molluscs, but Y.I. Starobogatov and his students in St Petersburg recognize 230 species in the same area. Localities for species known only from old records or empty shells need re-visiting. Molluscs are important in both aquatic and terrestrial ecosystems. Most consume plant and animal d‚bris, detritus and micro-organisms; many feed on green plants; carnivorous molluscs are also known. In turn, molluscs themselves are a significant component of the diet of some insects, fish, amphibians, birds and mammals. Oysters (Ostrea edulis), mussels (Mytilus galloprovincialis) and edible snails (Helix pomatia) have considerable economic importance. Centres for research on molluscs exist in Kiev (Institute of Zoology and Hydrobiology) and Sevastopol (Institute of Biology of Southern Seas); research groups also work in Simferopol University and Zhitomyr Teachers Training College. Terrestrial molluscs, freshwater gastropods, bivalves, and marine gastropods are studied most intensively. Information on their classification and recent distribution is published in the guidebook for the fauna of the Black and Azov seas, in several volumes of the serial monograph Fauna of Ukraine and in numerous papers. Recent reviews on lymnaeids and some families of marine bivalves are still lacking. Substantial mollusc collections are kept in the zoological museums of Kiev and Lviv. Another significant collection, including type specimens, is in the Institute of Zoology, Kiev. The main problems for these collections are insufficient finance, and a lack of qualified technical staff. The latest edition of the Red Data Book includes 12 species of molluscs (3 freshwater, 8 terrestrial and 1 marine). Pollution and environmental deterioration seem to be their biggest threat. The principal areas of endemism, Crimea and the Carpathians, need special attention and protection. Top priorities are to ensure support of collection development and computerization of the valuable information contained in museum archives. These will facilitate further research on mollusc diversity in Ukraine.