A unique pollen/spore flora from a lacustrine deposit overlying an 8 myr old basalt flow on the Northwestern Ethiopian highlands is described. A total of 126 pollen taxa is recorded. The pollen flora presents strong characteristics of a lowland rainforest and lacks the diagnostic elements of upland forests, the gymnosperms Podocarpus and Juniperus in East Africa. The commonest savanna element that characterizes the pollen diagrams from East Africa, the Gramineae, is very weakly represented. The pollen/spore diagram, which is constructed from 20 selected taxa, shows six distinct developments of the palaeovegetation during the deposition of the lake-beds. Semi-quantitative evaluation of the distribution of three diagnostic clay minerals shows developments parallel to that of the microflora. Kaolinite and illite are dominant in the humid pollen zone and an increase of smectite towards the end of the sedimentation period seems to agree with the observed general aridity trends in the clay mineral assemblages of equatorial zones towards the end of the Miocene. The flora most probably predates the Late Cenozoic global cooling and the Mediterranean desiccation. The northerly presence of lowland rainforest-type vegetation, as suggested by the composition of the Chilga palaeoflora, as recent as the latest Miocene is of great interest for the phytogeographic evolution of the continent.