In response to a growing need for statistically sound information on status and trends in the condition of the nation's ecosystems, the U.S. Environmental Protection Agency is developing and implementing the Environmental Monitoring and Assessment Program (EMAP). One component, EMAP-Surface Waters, will concentrate on lakes and streams. In its focus on lake condition at the regional and national scale, EMAP-Surface Waters will address concerns about the present extent and geographical distribution of lakes, their current ecological condition, the proportion that is degrading or improving, where, and at what rate, and the likely causes of adverse effects. The national design is based on a systematic grid of randomly placed points, so that conditions and trends can be estimated with known uncertainty. Lake condition will be assessed primarily through biological measurements; physical, chemical, and landscape information will be used to support and interpret conditions estimated by the biological indicators. In late summer of 1991, EMAP-Surface Waters will conduct a pilot lake assessment in the northeastern United States. This paper describes the EMAP design and indicators strategy tailored for lakes, with examples showing how these indicators can describe condition and trends at national and regional scales.