By using gas chromatography coupled with low- and high-resolution electron-impact mass spectrometry, low- and high-resolution chemical ionization mass spectrometry, and Fourier transform infrared spectroscopy, eight straight-chain aldehydes were identified in a water sample taken from the overflow pipe of a municipal sewer line that contained a combination of industrial and domestic sewage. This combination of infrared and mass spectral techniques yielded precise identifications of n-hexanal, n-heptanal, 2-heptenal, n-octanal, 2-octenal, n-nonanal, 2-decenal, and 2-undecenal. These findings were significant because few straight-chain aldehydes have been identified in the environment, and all those previously found were saturated.