Postharmostomum laruei McIntosh, 1934, utilizes terrestrial gastropods as first and second intermediate hosts. The flamed tigersnail, Anguispira alternata, is the only known first intermediate host. Among many reported second intermediate hosts, A. alternata is the most commonly reported and most heavily infected. The present investigation was undertaken to examine the breadth of second intermediate host use of P. laruei through experimental infections. Snails of 9 species were exposed to cercariae shed from infected A. alternata specimens in trials of varying durations. Developing worms were recovered from positive control A. alternata specimens, as well as members of 8 other species of terrestrial gastropods. Four of these (a succineid, Xolotrema fosteri, Oxychilus draparnaudi, and Neohelix albolabris) are new host records for P. laruei. The first record of incompatibility of P. laruei and potential second intermediate hosts is recorded, as members of the succineid and of X. fosteri were found to harbor dead worms at early stages of development. The ease with which P. laruei experimentally infects gastropods that are rarely found infected in the wild (e.g., N. albolabris, Webbhelix multilineata, Deroceras reticulatum), and even exotic snails (O. draparnaudi) combined with the seeming resistance to infection exhibited by other snails suggest that the specificity of host recognition is low, but also that both physiological incompatibility and ecological limitations restrict functional host use to A. alternata individuals in the wild.