These proceedings give a rather complete overview of the most recent research in the areas of fundamental processes and phase transitions, cloud droplet and ice nucleation in the atmosphere, and aerosol formation and aerosol characteristics in the atmosphere. Nine review papers on topics of special importance are supplemented by about 200 summaries on topics of greatest current importance. The volume should be of interest to scientists working in the atmospheric and environmental sciences, in chemistry and in physics, as well as to engineers working in these areas.