Project 4, Stream Flow Quality (B) Pesticides was designed to measure concentrations of pesticides in stream water leaving each of the eleven agricultural watersheds and calculate actual amounts of pesticides leaving in stream waters. Project 4B was inaugurated in 1974 and for one year a monitoring program was conducted on ambient concentrations of pesticides in streams. During the period 1975-1977 the monitoring program was expanded to cover a wider range of pesticides for both ambient concentrations in water and actual stream loadings in each of the eleven watersheds. This report summarizes the findings of pesticide losses in the agricultural watershed but does not infer that these materials will reach the Great Lakes.