PRCCM (Purdue Regional Climate and Chemistry Model), a 3-D regional-scale coupled atmosphere-chemistry model has been developed in order to contribute to improved simulations of transport, diffusion, deposition, transformation, and atmospheric effects of photochemical pollutants. Herein, the comprehensive three-dimensional Purdue Regional Model (PRM) is integrated with a photochemical module, which consists of the treatments of chemistry, emission and deposition. This integrated atmosphere-chemistry model performs photochemistry modeling and pollutant transport simultaneously with atmospheric dynamics modeling. The photolysis rate coefficients required to initiate photochemistry are derived on-line from short-wave radiation at each vertical level of the model domain within the radiation module. This feature enables tropospheric chemistry simulations to consider the physical properties of the atmosphere directly, including aerosol optional properties and cloudy-sky conditions. Meanwhile, the changes of atmospheric constituents from photochemical reactions also immediately affect radiation in atmospheric modeling. The integrated model, PRCCM, can provide accurate predictions of surface pollutant concentrations as well as the spatial pollutant distributions and transport at the regional scale by eliminating the possible errors and inconsistency between atmosphere and chemistry models. The feedback of tropospheric chemistry on regional climate can also be investigated using this model. Herein, a weekly simulation of a summertime ozone episode during July 16-22, 1998 in the Eastern U.S. has been carried out with this on-line atmosphere-chemistry model.