Elicitins are a family of structurally related proteins that induce hypersensitive response in specific plant species. Two Phytophthora infestans cDNAs, inf2A and inf2B, potentially encoding novel elicitin-like proteins, were isolated from a cDNA library made from infected potato tissue. Multiple sequence alignments and phylogenetic analyses of 19 elicitins and elicitin-like proteins from nine Phytophthora spp. and from Pythium vexans suggest that there are at least five distinct classes within the elicitin family.