A quasi-realtime calculation system for the global distribution of O3, NOx, HOx, and NMHCs by using a chemical AGCM for study of atmospheric environment and radiative forcing (CHASER) has been developed. The model is based on the version 5.4g of the Center for Climate System Research/National Institute for Environmental Studies (CCSR/NIES) AGCM. A7 days'forecast is executed once a day by using the NCEP reanalysed and forecasted dynamical field, and the model result is available on the WWW.