This report presents data summaries from three networks. Contour maps present NTN data. Concentration and deposition maps present MDN data. The line graphs present AIRMoN concentrations over time. The NTN maps portray spatial variability in the concentration and deposition of selected acids, nutrients, and base cations on regional and national scales. Only sites that meet prescribed data completeness criteria are included. In 2001, 193 sites met these criteria. Annual concentration or deposition values are printed next to each site. The concentrations are volume-weighted averages. The MDN maps show the concentration and deposition of total mercury in precipitation. Only sites meeting prescribed data completeness criteria are included. In 2001, 54 sites met these criteria. Annual concentration or deposition is printed next to each site. The concentrations are volume-weighted averages. The AIRMoN data shown by line graphs show AIRMoN concentrations over time. The time series graphs depict nine years (1993-2001) of data for six sites. Graphs for the Maryland (MD15) and Florida (FL18) sites begin in 1996 and 1997, respectively, when these sites completed their first full year of operation. The graphs show annual precipitation-weightedaverage concentrations of hydrogen ion, sulfate, nitrate, ammonium, and base cations. Base cations are defined here as the sum of calcium, magnesium, and potassium. concentrations are plotted in units of microequivalents/liter, which facilitates comparisons of how these chemicals relate to one another over the nine-year period.