The paper summarizes the first phase of an EPA sponsored research project to develop a manual-of-practice to investigate non-stormwater discharges of polluted waters into storm drainage systems. A number of past projects have found that dry-weather flows discharging from storm drainage systems can contribute significant pollutant loadings to receiving waters. If these loadings are ignored (by only considering wet-weather stormwater runoff, for example), little improvement in receiving water conditions may occur with many stormwater control programs. These dry-weather flows may originate from many sources, the most important sources may include sanitary sewage or industrial and commercial discharge cross-connections, failing septic tank systems in storm sewered areas, and vehicle maintenance activities. After the outfalls are identified that are affected by polluted dry-weather flows, additional survey activities are needed to locate and correct their sources.