This research has been carried out in Thuan Chau District in Son La Province (Northwest region of Vietnam) from May, 2010 to December, 2013. A survey of this region showed that there are 71 species and subspecies, belonging to 45 genera, 18 families and 2 subclasses of terrestrial snails living in this region. Snails of the Pulmonata subclass vary in number with 45 species, making up 63.38 percent of all species. In the Prosobranchia subclass there are 26 species, making up 36.62 percent of the total number of species. Terrestrial snails in Thuan Chau district are most diverse in terms of family and genera with the Cyclophoridae, Ariophantidae, Camaenidae, Subulinidae and Clausiliidae families dominating. The snails are distributed mainly in forests (69 species) and limestone mountain areas (44 species). Fewer species were found living on agricultural fields than in forests and limestone mountain areas (26 species). Species compo~ition differs with elevation with Tortaxis sp., Oospira abstrusa, Oospira smithi, Alycaeus requiescens and Cyclotus sp. being found only at elevations greater than 1000 meters.