With the aim of developing biomarkers of polycyclic aromatic hydrocarbon (PAH) genotoxicity for biomonitoring of the marine environment, the formation of DNA adducts and oxidative DNA damage was studied in the sentinel organism Mytilus. Mussels M. galloprovincialis were exposed for 21 d to different doses of benzo[a]pyrene (B[a]P) (50 and 100 mg B[a]P kg(-1) dry wt mussel d(-1)) via trophic intake. The kinetics of B[a]P concentration in whole mussel tissues was determined in both groups, and a dose-response study was conducted for both gill B[a]P-related DNA adducts and 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodGuo) formation in gill and digestive gland DNA. Exposure was followed by a 10 d depuration period to study mussel recovery. Although B[a]P was absorbed and bioaccumulated to very high concentrations (>300 mg B[a]P kg(-1) dry wt mussel), plateau values were not reached in either assay group. Regardless of the exposure dose of B[a]P, several bulky DNA adducts were induced in the typical PAH diagonal radioactive zone. For both doses, positive correlations were found between total DNA adduct level and both exposure time and B[a]P concentration in whole mussel tissues. DNA repair during depuration differed among the B[a]P-induced DNA adducts. B[a]P exposure had no effect on gill 8-oxodGuo levels, but led to a significant dose-dependent increase in the number of oxidative lesions in mussel digestive gland DNA. The decrease with depuration in digestive gland 8-oxodGuo levels to control values was indicative of the mussels' ability to recover from oxidative DNA damage.