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This paper presents the palynological results obtained from the Late Pleistocene deposits of Lake Magadi, Kenya (1-degrees-50’s, 36-degrees-18’E, 600 m), today located in the most arid region of East Africa. It documents the vegetational and climatic environment of the lake for two well defined periods: the Pleistocene-Holocene transition before 10 800 +/- 120 B.P., and the last glacial episode dated 17 710 +/- 220 B.P.. Compared with modern pollen data from the region, the microflora show the occurrence of an open vegetation. But the scarcity or absence of arid pollen indicators suggests more humid conditions than today, a conclusion that is confirmed by lithological and sedimentological analysis. The Holocene is missing and the most humid episode is registered between 12 000 and 10 000 B.P.. Highest allochtonous pollen input indicates an increased runoff, mostly related to higher rainfall during that period. The palynological results questionned the 17 000 B.P. C-14 ages for the bottom of the core.