This study assessed the sensitivity of Mytilus galloprovincialis (Mediterranean mussel) to UV-induced toxicity of pyrene, phenanthrene, fluoranthene and chrysene. Mussels were exposed to two different polyaromatic hydrocarbon (PAH) concentrations within the solubility limits for 7 days, after which the filtration rate and the blood cell stability of the mussels were determined to quantify the effects of PAHs. Mussel tissues were analysed at the end of the experiments to determine the degree of bioaccumulation of PAHs and in order to make quantitative body-burden/effect links. The differences between the tissue residue based effective concentration (TEC20/TEC50) values before and after ultraviolet (UV) exposure provided a measure of phototoxicity of the bioaccumulated PAHs. Out off the biomarkers applied, Neutral Red Retention (NRR) results showed that the most toxic compound is chrysene in the absence of UV. The NRR technique was found more sensitive compared to Fitration Rate (FR) technique. The toxicities of chrysene, phenanthrene and pyrene were enhanced by UV, while fluoranthene was toxic in the absence of UV lighting and its toxicity did not change by UV application.