A visualization study of pulsating laminar flows through U-tubes with a curved section of curvature radius ratios Rc=4, 9.5 and 29 is conducted in order to grasp the effects of Rc and flow parameters on their features. The instantaneous axial velocity profiles are visualized by hydrogen bubble method and are photographed at representative phases. The experiments are performed under the conditions of the Womersley numbers =5.5, 10 and 18 and the mean Dean numbers Dm=200 and 400, and the flow

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... ratios =0.5 and 1. Detailed descriptions are given of a depression and reversing phenomena in the velocity profile of the flow near the entrance and exit of the curved section and also in the downstream tangent, and the influences of Rc and on the flow characteristics are made clear. The flow patterns in the velocity profiles of Rc=9.5 similar to those in Rc=4 appear at smaller bend angle in the curved section and does at further station from the bend exit in the downstream tangent. The length required to recover a straight-tube flow in the downstream tangent is shorter than that of a steady flow with the same flow rate as the maximum one in the pulsating flow.