On Nov 1 and 2, 1993, at the World Health Organization's headquarters in Geneva, an international group of experts met to discuss the potential health impacts of climate change.The meeting was organised for the WHO Division of Environmental Health and was chaired by Dr Rudi Slooff of WHO. Their task is now to update and expand the 1990 WHO publication Potential Health Effects of Climate Change. They will also contribute to the work of the Intergovernmental Panel on Climate Change, especially to the working group on impacts of climate change. The proposed WHO publication is planned for 1995 and will include contributions on direct effects of increased temperatures on cardiovascular and cerebrovascular deaths besides potential impacts on vector-borne diseases, other communicable diseases such as cholera and algal biotoxin poisoning, effects on fresh water supply and food production, and impacts of a rise in sea level. Almost all these topics were covered in a Lancet series, that ends this week with the initiation of a discussion of questions to be tackled by the WHO group-namely, how to monitor possible health effects and what strategies are needed to prevent them.