The flow patterns in a stirred tank, 1m in diameter and 1 m in height, were studied using CFX, a commercial computational fluid dynamics program, with the impeller rotation speed, the impeller blade angle and the tankbottom shape varied and the baffles included or excluded. A vortex was observed in the center of the tank in the absence of the baffles, and the intensity of the vortex increased with increasing the rotation speed. The vortex was considerably reduced in the presence of the baffles. An increase in the blade angle increased the vertical flow and decreased the vortex intensity. The flow in the corners of the tank bottom turned smoother as the tank bottom was varied in shape from flat to round.