We have proposed a time-weighted measurement using blue rayon that selectively adsorbs and concentrates polycyclic aromatic hydrocarbons (PAH), e.g. benzo(a)pyrene (BaP). Though the method was demonstrated to be a convenient way to monitor PAH, the amount adsorbed to the blue rayon depends on the intensity of water stream and the level of PAH. The intensity of water stream was measured by 'plaster ball' method, while TWA of PAH in water was measured by a portable sampler using solid phase extraction cartridge. A level of BaP measured by the original blue rayon technique was corrected in this way by the water stream intensity, which correlated well with the TWA of BaP measured by the portable sampler. The improved blue rayon hanging method was applied to several field sites in the Seto Inland Sea of Japan. TWA of BaP ranged from 0.08 to 3.78 ng l-1. These results showed the possibility that the method could be used to evaluate pollution in aquatic environment.