Wet-only rainwater composition on a weekly basis was determined at four sites in West Java, Indonesia, from June 1991 to June 1992. Three sites were near the extreme western end of Java, surrounding a coal-fired power station at Suralaya. The fourth site was ∼100 km to the east in the Indonesian capital, Jakarta. Over the 12 months study period wet deposition of sulfate at the three western sites varied between 32-46 meq m-2 while nitrate varied between 10-14 meq m-2. Wet deposition at the Jakarta site was systematically higher, at 56 meq m-2 for sulfate and 20 meq m-2 for nitrate. Since sulfate and nitrate wet deposition fluxes in the nearby and relatively unpopulated regions of tropical Australia are both only ∼5 meq m-2 anthropogenic emissions of S and N apparently cause significant atmospheric acidification in Java. It is possible that total acid deposition fluxes (of S and N) in parts of Java are comparable with those responsible for environmental degradation in acid-sensitive parts of Europe and North America.