Climate change is a matter of concern to society, decision makers, and scientists. As part of the debate about the science of climate change, and in particular the extent to which current climate change is due to human activity or part of the natural variability of the global climate system, earth scientists try to understand how climates have changed in the past, and how past warming and cooling episodes affected the landscape and the plants and animals that occupied that landscape. It is also clear from the fossil record that past climate change has played a role in the evolution of animal and plant lineages, as well as plant and animal communities. Preserved in a series of lake deposits across northeastern Washington State, USA., to Smithers in north-central British Columbia, Canada, the Okanagan Highlands fossil deposits preserve a record of a time when the world was much warmer than now because of a naturally enhanced greenhouse effect, and the poles were ice-free and supported great forests. These sites are well known to fossil collectors for their beautifully preserved insects, fish, and plants. The Okanagan Highlands were an upland 50 million years ago, during the Early Eocene, and supported diverse forests swarming with insects and other animals that today are found in both temperate and tropical areas. The trees, shrubs, and herbs of these Eocene forests echo this pattern, including palms and bald cypress, together with spruce and birches. This special issue presents a series of papers that resulted from a symposium held in 2003 on the Okanagan Highlands that details the warm Eocene world of the interior uplands of northeastern Washington and British Columbia. Topics include reconstructing the landscape, biogeography, palaeoclimates, and fossil plants, insects, diatoms, and fish.