This is the first comprehensive land molluscs check list for Costa Rica, a previously poorly studied tropical country. It is based on a review of the literature from 1862 through 2001, excluding species not specifically reported for Costa Rica (e.g. those ambiguously reported for “ Central America”). There are a total of 183 species and subspecies reported (11 doubtful identifications), belonging to 25 families and 59 genera. The most diverse families are Spiraxidae with 33 (but 8 are doubtful identificartions) species and subspecies, Orthalicidae with 30 (1 is a doubtful identification), Subulinidae with 23, Helicinidae with 17 and Helicarionidae with 15. The groups with most urgent need for additional biodiversity study are the small species, specially the families Helicarionidae, Systrophiidae, and Zonitidae and the genus Spiraxis and Streptostyla.
Keywords: Land molluscs, check list, Costa Rica