Regular (non-alkylated) polycyclic aromatic hydrocarbons (PAHs) and their alkylated homologues were determined in sediments from Rodrigo de Freitas Lagoon using gas chromatography with mass selective detector (GC-MSD). Concentrations varying from 405 to 11734 ng x g(-1) were found for total PAHs (regular and alkylated homologues). The study showed a pyrogenic and petrogenic contribution, probably due to the incomplete burning of fossil fuels as a result of the intense traffic of boats and motor vehicles added to the anthropogenic activity of several gas stations present in the region of Rodrigo de Freitas Lagoon. According to the National Oceanic and Atmospheric Administration (NOAA) Sediment Quality Guide, PAHs concentration should not exceed 4000 ng x g(-1) (Long et al., 1995) The obtained data present values above the NOAA limit for some sampling points indicating chronic contamination of those sites probably due to anthropogenic activities related to petroleum and its derivatives.