Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous, persistent and toxic contaminants in the marine environment. Uptake of PAHs by marine deposit-feeding invertebrates can be determined by screening for PAH-derived metabolites. Methods for detection and quantification of PAH metabolites may serve as useful screening tools for preliminary stages of environmental risk assessment of PAH-contaminated sediment. Pyrene is one of the predominant pyrogenic PAHs and analysis of its metabolites provides an extra dimension to the environmental risk assessment of ecosystems with regard to PAH exposure, bioavailability and biotransformation. Measurement of pyrene metabolites, primarily 1-hydroxypyrene, in excretory products has gained considerable attention as a potential biomarker and is widely used to study PAH exposure in humans and animals. Reports on 1-hydroxypyrene as a biomarker for PAH exposure in marine invertebrates is on the other hand practically non-existing. The present study investigated formation of pyrene metabolites in the marine polychaete Nereis diversicolor, with special attention given to the detection of 1-hydroxypyrene. 1-hydroxypyrene was identified in tissues of Nereis diversicolor exposed to pyrene and various other PAHs, using Synchronous Flourescense Spectroscopy (SFS) and High performance liquid chromatography with fluorescence detection (HPLC/F). The study used a simple method that allows rapid determination of 1-hydroxypyrene in small samples of tissue from marine polychaetes and within this context the usefulness of SFS for identification and quantification was explored. Considering the complex composition of environmental PAH pollution, before the 1-hydoxypyrene in tissues of exposed marine invertebrates can be regarded as a suitable biomarker for assessing total PAH exposure, it is necessary to examine the following: (i) Relationships between 1-hydroxypyrene levels, parent PAHs accumulated in animal tissues, and corresponding total PAH exposure levels in sediment; and (ii) The degree of correlation between 1-hydroxypyrene levels and total PAHs levels in tissues of invertebrates. To develop such a biomarker, we quantified 1-hydroxypyrene and total PAH content in invertebrate tissues and studied the correlation between total PAHs and 1-hydroxypyrene concentrations. The total PAH content was measured by Gas Chromatography with Mass Spectrometry detection (GC/MS) and HPLC/F. The 1-hydroxypyrene formed in PAH exposed organisms was measured using SFS and validated by HPLC/F. The positive correlation between total PAHs and 1-hydroxypyrene concentrations in the polychaete tissues observed in our experiments, suggests the feasibility of 1-hydroxypyrene as a suitable biomarker for total PAH exposure assessment. Furthermore, the possibility of employment of the simple and rapid SFS method instead of HPLC/F for biomarker analysis has been confirmed by the positive and significant correlation between results achieved by these two analytical methods. Keywords: Sediment, PAH, Polychaetes, Metabolism, 1-hydroxypyrene, HPLC, SFS.