Two new corticolous lichen species are described, Lepraria nothofagi Elix & Kukwa (atranorin, strepsilin, porphyrilic acid) from Argentina and L. stephaniana Elix, Flakus & Kukwa (4-O-methylleprolomin, zeorin, salazinic acid, unknown terpenoid) from pre-Andean Amazon forest of Bolivia. In addition, the paper presents new records of 16 species of Lepraria from South America. Lepraria adhaerens, and L. diffusa are new to the Southern Hemisphere; L. borealis is new to South America; L. alpina is new to Chile, Colombia, Peru and Venezuela; L. caesioalba (chemotype I) is new to Venezuela, L. lobificans new to Argentina, L. pallida new to Peru, and L. sipmaniana new to Bolivia and Chile. The Chilean records of L. membranacea appeared to belong to L. sipmaniana. Therefore, the number of Lepraria spp. known at present from South America is enlarged to 27 species. 4-O-methylleprolomin is reported for the second time from lichens.