Topographic maps are commonly used to define populations of lakes in regional surveys of surface water quality. To illustrate the effect of diferent maps on that process, the authors compared the lakes represented on the 1:250,000 scale maps used for the Northeast Region of the Eastern Lake Survey - Phase I(ELS-1) to the lakes on the sample of large-scale maps. Lake areas at or near the lower limit of representation delimited 'smallest-lake' values for the compared 1:250,000-scale maps. Lake representation is influenced by cartographic limitations such as map scale, age, and complexity as well as the inherent variability of waterbodies. The total number of lakes on large-scale maps increased markedly as lake area decreased. Approximately 15,700 of the estimated 29,000 lakes in the EPA's Northeast Region were 1 to 4 ha in area.