Thirty species of Inoperculate Discomycetes are described herein from the Nahuel Huapí National Park (Argentina), distributed among thirteen genera belonging to the following families: Hyaloscyphaceae, Dermataceae, Sclerotiniaceae y Helotiaceae. Three of them, namely, Calloria, Sphagnicola and Phaeohelotium are recorded for the first time for Argentina. Of the thirty species found, fifteen are new records for this country. The following new combinations are proposed: Cyathicula chlorosplenioides (Speg.) Gamundí (basinym: Helotium chlorosplenioides Speg.); Rutstroemia megalospora (Speg.) Gam. (bas.: Helotium megalosporum Speg.) y Rutstroemia microsperma (Speg.) Gamundí (bas.: Helotium microspermum Speg.). The paper contains a critical study of type material from Spegazzini's herbarium, and the description of a new species of the same general area: Phaeohelotium castaneum. [ABSTRACT FROM AUTHOR]