During fiscal year 1995, the Atmospheric Sciences Modeling Division provided meteorological research and operational support to the U.S. Environmental Protection Agency. Operational activities consisted of the application of dispersion models, conduct of dispersion studies and model evaluations, and provision of advice and guidance. The research efforts emphasized the development and evaluation of air quality models using numerical and physical techniques supported by field studies, and conduct of studies under the High Performance Computing and Communications program. These efforts included the continued evaluation and application of ROM and RADM; development of Models-3; development of the RELMAP Mercury Model and RELMAP Dioxin Model; conduct of dense-gas dispersion and dry-deposition field studies; conduct of water channel studies of buoyant thermals in the atmosphere; data analysis of particle resuspension mass transport variability; examination of meteorology and acid aerosol concentration relationships; and statistical analysis of the global distribution of total column ozone.