The study is to analyze changes in monthly-averaged aerosol parameters derived from the SeaWiFS observations over East Asia from January 1998 through December 2004. All the SeaWiFS GAC Level 1 data (4 by 4 km spatial resolution data) that cover the Northeast Asian area were collected and processed by the standard atmospheric correction algorithm released by the SeaWiFS Project to produce daily aerosol optical thickness (AOT) and Angstrom exponent imageries. Cloud screening was applied if AOT at 490 predicted from the aerosol look-up tables embedded in the algorithm exceeded 0.7. From the daily composite images, monthly average AOT and Angstrom exponent values were extracted for each one of the six study areas chosen from the surrounding waters of Japan. The results showed that, although annual mean of AOT did not show any trend, +0.01-0.015 increase in Angstrom exponent in almost all study areas was observed over the study period. This increase is interpreted as 4-5% increase in submicron fraction (SMF), or the ratio of contribution of submicron aerosol particles to the total AOT, and will be interpreted as an increase of submicron particles due to the enhanced anthropogenic activities in East Asia.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.