Investigations of the sedimentary rocks of the Umkondo system have enabled six zones of eastwardly increasing metamorphic grade to be delineated on the basis of index mineral assemblages in pelite horizons. Chlorite, garnet (almandine), staurolite, kyanite, and sillimanite isograds have been recognized over a distance of 500 km. along the eastern border of Southern Rhodesia and are plotted on a map. More detailed reconnaissance work has been confined to the Barue highlands north-east of Inyanga. In addition, a 'zone of intermediate isotopic age measurements' is proposed to the west of the lowermost chlorite zone. The isograds lie parallel to the structural edge of the north-south trending Mozambique orogenic belt and can be joined with those of similar metamorphic rocks in the east-west trending Zambesi orogenic belt, suggesting contemporaneity of the c. 500 m.y. regional tectono-thermal event in these two belts.