The taxonomy of the Alternaria spp. has been a subject, of controversy because of their high variability in conidial morphology and polymorphism displayed even in pure cultures. The published Korean literature on the genus Alternaria is scattered and fragmentary, and pertains to about 25 species with special emphasis on occurrence and pathogenicity, but mycological studies on this group of fungi are insufficient. This is the first series of detailed and consolidated account of Korean species of Alternaria, which includes 11 species; viz., Alternaria brassicae, A. brassicicola, A. cinerariae, A. dauci, A. dianthi, A. dianthicola, A. helianthi, A. helianthinffciens, A. iridicola, A. japonica and A. protenta. Detailed diagnostic descriptions, specific characterizations, taxonomic discussions and illustrations for each species are presented.