The sterol composition, including the fecal biomarker coprostanol, from a variety of sample types was determined by capillary gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The coprostanol concentration in field samples readily provided an estimate of human fecal pollution. The technique was successfully used for stormwater, the sea-surface microlayer, beach sands and greases, and in regional studies of coastal sediments. Sterol profiles can be used to distinguish human and non-human sources of sewage pollution and algal blooms. Development of appropriate component ratios, both within the sterol fraction and between compounds classes, may provide a useful mechanism to further exploit sterol data. For sewage-containing samples, it may be possible to extend the data comparison, and calculation of key ratios, to include bacteriological parameters. Collectively, the use of sterol compositional data can complement other physical, chemical and biological measurements obtained in environmental studies.