To clarify the flow in the swirl chamber of a diesel engine, numerical prediction and measurement were performed. The flow model was based on the solution of the finite difference form of the governing differential equations for the transport of mass and momentum, including the concept of the turbulent effective viscosity. To facilitate flow analysis and measurement, swirl chamber flow was assumed to be two-dimensional. Special emphasis was placed on the effects of swirl chamber geometry and the connecting passage. The predicted results were confirmed in experiments using a special air model. Then, flow characteristics in the swirl chamber of a full scale engine were predicted. The results show that swirl chamber geometry and the connecting passage have significant effects on the flow characteristics, such as the tangential velocity and the swirl formation.