The purpose of this research project is to determine the spatial pattern of wet deposition in North America during 1987 and to investigate trends in wet deposition in North America from 1979 through 1987. The project considers precipitation-weighted average concentration and deposition for nine ion species: hydrogen ion, sulfate, nitrate, ammonium, calcium, chloride, sodium, potassium, and magnesium. To accomplish the research an Acid Deposition System (ADS) data base has been established that integrates wet deposition monitoring data from several regional and national monitoring networks. Networks included are the National Atmospheric Deposition Program/National Trends Network (NADP/NTN), the MAP3S precipitation chemistry network, the Utility Acid Precipitation Study Program (UAPSP) network, the Canadian Precipitation Monitoring Network (CAPMoN), and the daily and 4-weekly Acidic Precipitation Monitoring in Ontario Study networks (APIOS-D and APIOS-C). The ADS data base and statistical summaries are available to others to conduct additional research studies.