The origin of paraffin from penile granuloma tissue was determined first by field desorption mass spectrometry. A case of penile granuloma with histopathological findings of sclerosing lipogranuloma is presented. Chemical composition of the lesional lipid by elemental analysis and infrared absorption spectroscopy revealed paraffin hydrocarbon. Field desorption mass spectrometric analysis showed the paraffin to be a mixture of saturated hydrocarbons containing substantially 24 to 40 carbon atoms. On the basis of the chemical structure of naturally occurring lipids we concluded that this paraffin was exogenous and not endogenous material that was produced in the tissue following lipid degeneration.