The classification of Pleosporales has posed major challenges due to the lack of clear understanding of the importance of the morphological characters used to distinguish between different groups in the order. This has resulted in varied taxonomic treatments of many families in the group including Melanommataceae and Lophiostomataceae. In this study we employ two nuclear DNA gene markers, nuclear ribosomal large subunit DNA and translation elongation factor 1-alpha in order to examine the molecular phylogenetics of Pleosporales with strong emphasis on the families Melanommataceae and Lophiostomataceae. Phylogenetic analyses recovered Melanommataceae, Lophiostomataceae, Hypsostromataceae, and a few others as strongly supported clades within the Pleosporales. Melanommataceae as currently circumscribed was found to be polyphyletic. The genera Byssosphaeria, Melanomma, and Pseudotrichia were recovered within the family, while others such as Ostropella and Xenolophium nested outside in a weakly supported group along with Platystomum compressum and Pseudotrichia guatopoensis that may correspond to the family Platystomaceae. The genus Byssosphaeria was recovered as a strongly supported group within the Melanommataceae while Melanomma was weakly supported with unclear relationships among the species. The genera Herpotrichia and Bertiella were also found to belong in the Melanommataceae. Lophiostomataceae occurs as a strongly supported group but its concept is here expanded to include a new genus Misturatosphaeria that bears morphology traditionally not known to occur in the family. The strongly supported clade of Misturatosphaeria contains nine species that have gregarious, papillate ascomata with lighter coloured apices and plugged ostioles and that vary in ascospore morphology from 1- to 3-septate to muriform. Along with a strongly supported Lophiostoma clade, also within the family are Thyridaria macrostomoides based on new sequences from Kenyan collections and Massariosphaeria triseptata, M. grandispora, Westerdykella cylindrica and Preussia terricola based on GenBank sequences. The family Hypsostromataceae was recovered as a strongly supported monophyletic group nested within the Pleosporales.