The family Microthyriaceae sensuLumbsch and Huhndorf 2010 is a poorly known but interesting family comprising 50 genera consisting of foliar epiphytes or saprobes on dead leaves and stems. We re-visited the family based on examinations of generic types where possible. Members are distributed in Aulographaceae, Asterinaceae, Microthyriaceae, Micropeltidaceae and Palmulariaceae and notes are provided on each of these families. Nine genera are transferred from Microthyriaceae to Asterinaceae, and two to Aulographaceae based on the splitting or dissolving nature of the thyriothecia to release ascospores. New sequence data for a number of species and genera are provided. Microthyriaceous members growing on other fungi and lichens differ from Microthyriaceae sensu stricto and the family Trichothyriaceae is reinstated to accommodate these taxa. Other genera of Microthyriaceae belong in Rhytismataceae, Stictidaceae, Venturiales incertae cedis, Dothideomyetes genera incertae cedis, Hypocreales incertae cedis and Ascomycota genera incertae cedis. The family Microthyriaceae is reduced to seven genera characterised by superficial, flattened thyriothecia, with the cells of the upper wall radiating in parallel arrangement from the distinct central ostiolar opening, while the lower peridium is generally poorly developed. Sequence data is provided for five species with thyriothecia and Paramicrothyrium and Neomicrothyrium are described as new genera and Micropeltis zingiberacicola is introduced as a new species. Our phylogenetic analysis underscores the high genetic diversity for thyriotheciate species and there is no clear clade that can be well defined as Microthyriales. Nuclear ribosomal data support multiple polyphyletic lineages within Microthyriaceae and Micropeltidaceae. Some unexpected DNA based phylogenetic relationships such as those between Muyocopron and Saccardoella will require corroboration with more complete taxon sampling as well as additional non ribosomal markers. There are few differences between Aulographaceae, Asterinaceae and Palmulariaceae and these families may need synonymising.