We have developed a new regional climate model based on the Regional Atmospheric Modeling System (RAMS), and conducted present and future Asian regional climate simulations nested in the CCSR/NIES Atmospheric General Circulation Model (AGCM). The general simulated features of the AGCM and some regional phenomena such as orographic precipitation, which were notappeared in the outcome of the AGCM simulation, were successfully produced by the nested regionalclimate model. Annual mean precipitation, evapotranspiration and surface runoff are projected to increase in a lot of Asian regions. Those indicate faster and stronger hydrological cycles. There is growing apprehension that the risk of floods will increase under the global warming and the associated hydrological changes such as the intensification of convective precipitation in summer, the reduction of snow cover in winter, and earlier snow melting in spring.