Reports on the results of water quality testing by citizen volunteers in a pilot project initiated in July 1985 by the Alliance for the Chesapeake Bay under a public participation grant from the U.S. Environmental Protection Agency. Among other goals, the project was designed to explore the feasibility of and reliability of monitoring by volunteers. Two Chesapeake tributaries, the James River in Virginia and the Patuxent River in Maryland, were included in the project. The report describes the organization and administration of the project, outlines sampling methods used, and compares water quality data collected by volunteers with those obtained in State programs. Data are summarized in Appendix I of the report; site-specific data are available in Appendix II, published as a separate volume.