It has been assumed that acid rain is predominantly a problem of long-range transport of pollutants from large fossil fuel combustion sources, namely coal-fired utilities. However, close examination of fuel use information and source emission characteristics in the Adirondacks, Florida, and California suggests that local oil burning and automotive sources may be major contributors to the occurrence of acid rain in these areas. This report describes the possible role of local combustion sources in the production of acid rain, discusses the implications of the findings, and their relevance to alternative control strategies for acid rain. Oil-fired boilers, especially the smaller commercial, industrial, and residential units, produce at least 3 to 10 times as much primary sulfate per unit of sulfur content as coal-fired units. Moreover, oil-fired units emit comparatively large quantities of catalytic compounds capable of rapidly converting still more sulfur oxide to sulfate in the atmosphere. Thus, in areas where large quantities of oil are burned, the direct impact from locally generated sulfates may equal or even exceed that produced by imported sulfates derived from distant coal-burning sources. Fuel consumption data show that large quantities of oil are being consumed in areas experiencing acid rain. Forty percent of the residual and 36 percent of the distillate oil burned in the United States is consumed in the eight-state area surrounding the Adirondacks. California is the next largest oil-consuming area and Florida is third. Nitric acid is responsible for about 30 percent of rainfall acidity in the Northeast and Florida, and for about 30 to 75 percent of the rainfall acidity in California.