The beaches along the Lake Huron shoreline are amongst the most popular in southern Ontario, drawing vacationers from across Ontario and the Northern United States. The main resort areas are places such as Port Franks, Grand Bend, Bayfield, Goderich, Bruce Beach, Kincardine, Inverhuron, Port Elgin, Southampton and Sauble Beach. Tourism is a multi-million dollar industry in this area. In 1983, a number of beaches along the Lake Huron shoreline were posted because of elevated bacterial concentrations. Some survey work was initiated during the summer of 1983 at Grand Bend to obtain preliminary information on bacterial sources. However, few conclusions could be reached, and it was decided to carry out a more detailed investigation during 1984. This report outlines the summary results of the 1984 investigation.