The objective of this NATO Advanced Research Workshop was to discuss our current understanding of the role of clouds in climate and chemistry. The range of topics dis cussed during the workshop included: modeling of clouds in GCMs; observations of the cloud micro physical properties; the water vapor cycle; troposphere-stratosphere exchange; role of in-cloud transport in tropospheric ozone; regulation of current and paleo climate by clouds; and anthropogenic sulfate aerosols and modification of cloud properties. The essence of the discussions is captured in the accompanying summary by the...