Precipitation composition was characterized at 14 remote sites between 65 degree N and 51 degree S. Anthropogenic sources contributed to non-sea-salt (nss) SO sub(4) super(2-), NO sub(3) super(-), and NH sub(4) super(+) in North Atlantic precipitation. Biogenic sources accounted for 0.4-3.3 mu eq L super(-1) of volume-weighted-average (VWA) nss SO sub(4) super(2-) in marine precipitation. SO sub(4) super(2-) at the continental sites (2.9-7.7 mu eq L super(-1)) was generally higher. VWA NO sub(3) super(-) (0.5-1.3 mu eq L super(-1)) and NH sub(4) super(+) (0.5-2.6 mu eq L super(-1)) at marine-influenced, Southern Hemispheric sites were generally less than those at continental sites (1.4-4.8 mu eq L super(-1) and 2.3-4.2 mu eq L super(-1), respectively). VWA pH ranged from 4.69 to 5.25. Excluding the North Atlantic, nss SO sub(4) super(2-), NO sub(3) super(-), and NH sub(4) super(+) wet depositions were factors of 4-47, 5-61, and 3-39, respectively, less than those in the eastern United States during 2002-04. HCOOH sub(t) (HCOOH sub(aq) + HCOO super(-)) and CH sub(3)COOH sub(t) (CH sub(3)COOH sub(aq) + CH sub(3)COO super(-)) concentrations and depositions at marine sites overlapped, implying spatially similar source strengths from marine-derived precursors. Greater variability at continental sites suggests heterogeneity in terrestrial source strengths. Seasonality in deposition was driven by variability in precipitation amount, wind velocity, transport, and emissions. Between 1980 and 2009, nss SO sub(4) super(2-) at Bermuda decreased by 85% in response to decreasing U.S. SO sub(2) emissions; trends in NO sub(3) super(-) and NH sub(4) super(+) were inconsequential. Corresponding decreases in acidity, as reflected in the significant 30% decline in VWA H super(+), impacted pH-dependent chemical processes. Comparisons between measurements and models indicate that current predictive capabilities are uncertain by factors of 2 or more.