Ongoing research conducted by the Welsh Language Research Unit of Cardiff, Wales is described. This research has concentrated mainly on recording and describing the phonology of some varieties of Welsh spoken in South-East Wales, particularly as it is associated with geographic areas and affected by population changes resulting from industrial development. The phonology of the dialects under study is compared and described in some detail. Tables illustrating the dialectal variations are included, as is a list of unpublished dissertations from the University of Wales on which the present work was based. (PM)