ABSTRACT: We studied the temporal variation of polycyclic aromatic hydrocarbons (PAH) levels in the wild mussel Mytilus galloprovincialis, water and sediment from 3 sampling sites on the Galician coast of Spain between the rias of Arousa and Muros, which were dramatically affected by the large oil spill from the oil tanker ‘Prestige’. The samples were collected periodically, from November 22, 2002, 3 d after the tanker sank, until December 23, 2003. The total hydrocarbon content in the water and sediment samples was determined by fluorescence and expressed as concentration of chrysene. In addition, individual PAHs—analytes recommended by the US Environmental Protection Agency—were analysed in the mussel samples by HPLC using fluorimetric detection. A maximum concentration of 2.07 × 10³ µg equiv. of chrysene l^–1 was found in the water column at the sampling site of Furnas on November 29, 2002 which decreased to 0.21 µg l^–1 by October 2003. Likewise, the concentrations of the sum of the 16 PAHs determined in the mussel samples collected at the sampling points were between 2.5 × 10³ and 5.9 × 10³ µg kg^–1 dry weight in the days immediately following the oil spill and then decreased to 0.13 × 10³ µg kg^–1 in October 2003. However, no relevant information could be obtained from the PAH content of the sediment samples. A relation between parent PAHs accumulated in the mussels and their molecular weight (MW) has been found to provide an indication of hydrocarbon pollution. A good approximation was obtained when the total PAH content (ΣPAH) was represented versus the ratio of low MW PAHs to high MW PAHs (ΣLPAH:ΣHPAH). When the depuration rate r of individual PAHs by the mussels was fitted to an exponential model, 2 different values of r were found depending on the PAH concentration. The change from a slow to fast depuration rate was produced when the logarithm of the concentration was 1.0.