Blue mussels, Mytilus edulis, were collected in Osaka Port, Kyoto Maizuru Bay and Hokkaido, Japan, and analyzed with a fluorescence spectrophotometer followed by fluorescence-HPLC on a C-18 reversed-phase column to examine environmental contaminants in the samples from each location. The fluorescence (Em λmax=ca. 350nm) and excitation spectra (Ex λmax=ca. 310nm) of samples obtained from different areas were similar. The ratios of fluorescence intensity of the samples from Osaka Port and Kyoto Maizuru Bay to that of samples from the environmentally clean coast of Hokkaido were ten and five to one, respectively. The levels of individual polycyclic aromatic hydrocarbons (PAHs) ranged from 66ppb for pyrene to 1.3ppb for benzo (a) pyrene in mussels from Osaka Port as determined by HPLC. On the other hand, the maximum concentrations in mussels of unknown fluorescent substances in the samples from Osaka Port and Hokkaido were 1600ppb and 20ppb, respectively, when picene was adopted as standard. These results suggest that the developed method can be used to monitor changes of the marine environment by the use of fluorescent substances as indicators.