A pollen diagram from Lake Monticchio, a volcanic crater lake in S Central Italy east of Naples, shows a long vegetation record for the Holocene and the later portion of the Last (Weichselian) Glacial Period. The upper 735 cm of a 2550-cm core is assigned to the Holocene. It begins with expansion of Betula (birch) and Quercus (oak), followed by Fagus (beech), Tilia (lime) and other mesic trees. In the next phase the flora is dominated by oak with an increase in herb pollen. In the later Holocene the flora is again diversified by the appearance of Abies (fir), Curpinus (hornbeam) and other trees. In the latest Pleistocene portion of the core the vegetation is dominated by grasses, Artemisia (sage-brush) and chenopods, indicating a treeless environment. The base of the core shows continued dominance by steppe-like vegetation with 'interstadial' episodes in which trees, especially oak, beech and fir, were abundant. The climatic interpretation is that the late Pleistocene was very dry, at least in the summer growing season, and probably, although not necessarily, colder than now. In the Holocene increased precipitation favoured expansion of tree populations. For a brief period there was a return of water stress in the growing season marked by a loss of tree species diversity and an increase in herbs. In the later Holocene a progressive diversification of tree species indicates a return to a more humid and perhaps cooler climate. The vegetation history and climatic inferences are closely similar to records available from Greece. The available radiocarbon dates, which show a consistent pattern, indicate that the core is much older than 40000 years at the base but not old enough to include the major post-Eemian interstadials. The 'Holocene' birch expansion began nearly 20000 years ago. These dates appear to be systematically too old in the light of present knowledge. The preliminary character of the study is emphasized. Further radiocarbon dates, especially of the 'Holocene' section, are needed, as are more detailed studies of sedimentation processes and tephra occurrences.