The investigation comprises sampling and testing of small streams receiving treated sewage effluents, effluents from septic tanks at farmhouses, and drainage water from fields amended with manure or sludge. There was none or very little estrogenic activity in the stream water samples or in the field drain water samples. In contrast to this, the estrogenic activity in septic tank effluents was high, and a significant dilution is required to reduce the activity to below known biological effect levels.