Three-dimensional viscoelastic flows in a rectangular channel with a cavity were studied both numerically and experimentally. In the numerical study, computations were carried out using the Phan-Thien-Tanner (PTT) model as a constitutive equation. A finite volume method (FVM) using colocated grids was applied. A three-dimensional structure in the cavity was observed even when three-dimensional behavior was not remarkable in main flows. At high Weissenberg number, the flow in the cavity spirals to move towards the center plane of the channel. In the experiments, the flow of polymer solutions was visualized to observe three-dimensional flow behavior near the cavity part. It was confirmed that the spiraling flow moving towards the center plane emerged in the cavity. (C) 2003 Elsevier B.V. All rights reserved.