A synopsis of 26 species belonging to 10 genera of Caliciales (s.lat.) occurring in Costa Rica is given. Short comments on the ecology and distribution of the species, indications of occurrence of secondary substances, and observations on the ultrastructure of the spores in some species are included. The mainly tropical genera Pyrgidium, Schistophoron and Tylophoron are given particular attention. Seventeen species are new to Central America and the following five new to science: Caliciurn constrictum sp. nov., Chaenothecopsis rubina sp. nov., Coniocybe sanguinea sp. nov., Schistophoron variabile sp. nov., and Tylophoron crassiusculum sp. nov. Two new combinations, Mycocalicium albonigrum (Nyl.) comb. nov. and Pyrgidium montellicum (Beltr.) comb, nov., are made. Lectotypes have been designated for Tylophoron annulatum Krempelh., T. cupulare Vainio, T. moderatum var. consociata Vainio and T. rufocapillatum Nádv. Names of several taxa in Pyrgidium and Tylophoron have been put into synonomy. Arthothelin, thuringione and thiophanic acid (in Calicium hyperelloides Nyl.) and lecanoric acid, 2'-O-methylperlatoic acid and lichexanthone (in Tylophoron) are reported for the first time in the Caliciales.