The Eastern Lake Survey was conducted by the US EPA in the fall of 1984. Lakes were selected at random, based on a rigorous statistical design that permits estimates of the chemical and physical status of lake populations in specified regions of the survey. Complete chemical characterization was performed on water samples from each lake and a detailed quality assurance and quality control program was an integral part of the study and resulting data base. Three regions of the Eastern U.S. were defined (Northeast, Upper Midwest, and Southeast) in which a total of 1612 lakes was sampled. In the Northeast, 4.6 percent (326 lakes) were estimated to be acidic (i.e., acid neutralizing capacity (ANC) < or = to 0.0 micro eq/l), while 60 percent (4258 lakes) had ANC < or = to 200 micro equiv/l. In the Upper Midwest, 1.7 percent (148 lakes) were estimated to be acidic, with 41.4 percent (3518 lakes) having ANC < or = to 200 micro equiv/l. The unique survey design provides a framework for interpreting current and future aquatic research on regional basis.