Despite more than half a century of research, the evolutionary origin of termites remains unresolved   . A clear picture of termite ancestry is crucial for understanding how these insects evolved eusociality, particularly because they lack the haplodiploid genetic system associated with eusocial evolution in bees, ants, wasps and thrips  . Termites, together with cockroaches and praying mantids, constitute the order Dictyoptera, which has been the focus of numerous conflicting phylogenetic studies in recent decades       . With the aim of settling the debate over the sister-group of termites, we have determined the sequences of genes encoding 18S ribosomal RNA, mitochondrial cytochrome oxidase subunit II (COII) and endogenous endo-beta-1, 4-glucanase (EG) from a diverse range of dictyopterans. Maximum parsimony and likelihood analyses of these sequences revealed strong support for a clade consisting of termites and subsocial, wood-feeding cockroaches of the genus Cryptocercus. This clade is nested within a larger cockroach clade, implicating wood-feeding cockroaches as an evolutionary intermediate between primitive non-social taxa and eusocial termites.