Citizen activists participate year after year in the Illinois Volunteer Lake Monitoring Program—providing their own boating equipment and collecting data at least twice monthly from May through October. Over two thirds of the volunteers who started in 1981 continue to be active. The program was initiated by the Illinois EPA in 1981 to help citizens make more informed decisions about lakes' use, protection, and management. Citizens are trained to measure Secchi disk transparency and total depth and record field observations in a systematic manner at designated sites. Secchi disks, special data reporting forms, and postage paid envelopes are provided by the Agency. Morphological data and assessment information are also collected for the lake and watershed. The sampling data are computerized and a statewide summary report is prepared. As resources permit, individual lake reports are also prepared which incorporate physiochemical data obtained under the Agency's Ambient Lake Monitoring Program and include general recommendations for lake protection and management. The program has been very successful: 141 volunteers participated in monitoring 87 lakes in 1981; in 1983 approximately 240 volunteers are scheduled to monitor 160 lakes. The program provides the volunteers with current data on their lake and how its transparency compares to other lakes in the State. It also provides a historic data base for determining seasonal and long-term trends in lake quality. The volunteer monitoring program has resulted in implementation of lake protection/restoration measures for several lakes. Federal, State, and local agencies have used the data collected to help assess the severity of water quality impacts from agricultural runoff and target resources for water quality benefits. Volunteer data have helped document water quality problems, point out critical areas most responsible for water quality degradation, guide the implementation of lake protection/management techniques, and evaluate their effectiveness.