Distributional and taxonomic information on flightless insects were used in a cladistic analysis of distributions and endemism (CADE) to generate a testable hypothesis of area-relationships for the central eastern African mountains. A tree was obtained where the relationships of all mountain areas were resolved according to a hierarchical, time-dependent sequence of vicariance events. It is inferred that most of the present species distributions originated as a consequence of forest fragmentation during the Pleistocene cycles of cooling and drying of the climate. Around 150 000–130 000 years ago, Africa experienced colder, dryer conditions than present conditions. This could have been the first stimulus in the last glacial/interglacial cycle for a large vicariance among different mountain systems. About 130 000 years ago, a warmer, moister phase than the present began, and this condition could have represented an important occasion for the widespread distribution of some genera and species among neighbouring mountain systems. The last glacial maximum confined most species to single refugial montane areas. A resumption of warm, moist conditions probably led up to the Holocene ‘optimum’ of greater rainforest extent allowing some species to disperse again among adjacent mountain peaks.