Organic compounds were isolated from grab or composite samples of industrial and municipal discharges and of the Illinois River by liquid-liquid extraction or adsorption on activated carbon or XAD-2 resin columns. Of the 213 different compounds identified and semiquantitated by gas chromatography-mass spectrometry in 16 samples, 74 were long-chain hydrocarbons or their derivatives. Although their toxicological significance in the environment at the levels found is unknown, the widespread presence of these cocarcinogens and promoters (often found in conjunction with known initiators) may make them significant environmental toxicants. Some evidence for this is the fact that serial dilutions of the extracts were highly toxic to Salmonella typhimurium in the Ames assay, while weak mutagenicity was occasionally detected.