The geochemistry of organic sulfur in a suite of samples covering the upper 100 m of sediment from the Peruvian margin has been characterized by elemental analysis, X-ray absorption spectroscopy and analytical pyrolysis. These data are compared with those obtained from a thermally immature, but consolidated, sulfur-rich sediment (Miocene Monterey Fm, CA). Results indicate that sulfur incorporation into organic matter takes place primarily within the upper few meters of sediment, but sulfur in-growth continues at greater depths. The close similarity in organic sulfur composition for these samples lends support for the premise that the Peru margin is a modern analogue of the Monterey Fm.