Several studies have recently emphasized the merits of using coprostanol, a major human fecal sterol as a positive molecular marker of domestic pollution in addition to the standard method for enumeration of fecal coliforms. Bunch and his coworkers (1967) have shown that coprostanol as well as other sterols can be removed from wastewater by an adequate secondary sewage treatment. This study was undertaken to estimate the extent of human and warmblooded animal fecal pollution and to pinpoint the main sources of this pollution within a 3 mile radius of Burlington, Iowa on the Mississippi River. The survey covered seven sampling points, including raw sewage to the Burlington Wastewater Treatment Plant, the effluent and surface water up and down stream from the treatment plant outfall. The analytical method used for the estimation of the coprostanol was based on the methodology which was previously developed by Murtaugh and Bunch and proven effective for the recovery of sterols from wastewater as well as from a stream in the Cincinnati, Ohio area. The procedure consists of hexane extraction, mild alkali-alcohol hydrolysis of esters and conjugates to free parent sterols, cleanup by thin-layer chromatography (TLC) and quantitative measurement by gas-liquid chromatography (GLC). Simultaneously with the assay for the fecal sterol, the number of fecal coliforms were determined utilizing the membrane filter technology.