To resolve relationships between members of the family Thermomonosporaceae, phylogenetic analyses using three sets of nucleotide sequences from 16S rDNA, 23S rDNA and the 16S-23S internal transcribed spacer (ITS) were carried out. Nearly all species of the family were included in this study. On the basis of congruous phylogenetic results and chemotaxonomic data, the following proposals are made. First, Actinomadura libanotica, Actinomadura aurantiaca, Actinomadura glomerata and Actinomadura longicatena are transferred to the genus Actinocorallia as Actinocorallia libanotica comb. nov., Actinocorallia aurantiaca comb. nov., Actinocorallia glomerata comb. nov. and Actinocorallia longicatena comb. nov., respectively. All the species of this genus are phylogenetically coherent and of phospholipid type PII (presence of phosphatidylethanolamine), distinguishing them from other Actinomadura species that are of phospholipid type PI (absence of diagnostic phospholipids). Second, Excellospora viridilutea is transferred to the genus Actinomadura as Actinomadura viridilutea comb. nov. As a result of the proposed transfers, the family Thermomonosporaceae now contains four genera Thermomonospora, Actinomadura, Actinocorallia and Spirillospora. The genus Actinocorallia and family Thermomonosporaceae are redescribed.