Information is needed with respect to the tolerable levels of development, chemical inputs, bacteria and organic materials that a lake basin can withstand before water quality is impaired, to provide the basis for regulations that will foster the maintenance of high lake water quality and natural surroundings. In 1972, a three-year project was undertaken to help solve the problems of Squam Lake, New Hampshire and provide an approach for coping with similar pressures on other recreational waters. Data on the water quality of the lake were obtained with respect to light penetration, temperature, dissolved oxygen, total phosphates, nitrates and total coliform. The status of the lake was examined in terms of species diversity of plankton, using the Shannon-Weiner diversity index. Sources of pollution and contamination were located by a systematic method of water analysis. As sources were located, this information was given to the respective town health officers who in turn continued the investigation to eliminate the sources of pollution. (Modified author abstract)