Ghana-Togo-Mountain Languages: a socio-cultural, a typological or a genetic grouping?

This article provides a synoptic view of research that has been carried out over the centuries on the fifteen languages that are spoken in the Ghana-Togo hills of West Africa with an outlier in Benin. It traces the dilemmas and opportunities the languages offer for historical, descriptive and theoretical linguistics. It highlights some of the developments in the recent investigations that have taken place and concludes with an overview of the articles on GTM languages in the issue.