The classification of subclass Xylariomycetidae is revisited with additional collections and phylogeny based on novel rDNA sequence data. Phylogenetic inferences are provided and are based on analysis of 115 sequence data, including new data for 27 strains. An updated outline to the subclass is presented based on the phylogenies and comprises two orders, 18 families and 222 genera. An account of each order, family and genus in the subclass is given. We accept the orders Amphisphaeriales and Xylariales based on morphological and phylogenetic evidence. Amphisphaeriales comprises Amphisphaeriaceae, Bartaliniaceae fam. nov., Clypeosphaeriaceae, Discosiaceae fam. nov., Pestalotiopsidaceae fam. nov. and Phlogicylindriaceae fam. nov. Xylariales comprises Apiosporaceae, Cainiaceae, Coniocessiaceae, Diatrypaceae, Graphostromataceae (doubtful), Hyponectriaceae, Iodosphaeriaceae, Lopadostomaceae fam. nov., Melogrammataceae, Pseudomassariaceae fam. nov., Vialaeaceae and Xylariaceae. The new genera and species introduced are Arthrinium hyphopodii, A. subglobosa, Cainia anthoxanthis, Ciferriascosea gen. nov., C. fluctamurum, C. rectamurum, Discosia neofraxinea, D. pseudopleurochaeta, Hyalotiella rubi, Seimatosporium cornii, S. ficeae, S. vitis and Truncatella spartii.