The eects of mean ¯ow three-dimensionality on the turbulent structure of the boundary layer on a swept wing are investigated experimentally. The con®guration of the test model used to simulate the in®nite swept wing condition is similar to that used by Van den Berg, B., Elsenaar, A., Lindhout, J.P.F., Wesseling, P., 1975. Measurements in an incompressible three-dimensional turbulent boundary layer, under in®nite swept-wing conditions, and comparison with theory. J. Fluid Mech. 70 (1), 127±148. Mean ¯ow measurements show that the location of the maximum cross-¯ow velocity is within the log-law region for the streamwise velocity pro®les. In the near-wall region, the streamwise turbulence intensity, u 2 p aU s , decreases with increasing three-dimensionality. A four quadrant analysis is applied to the ¯uctuating velocity components in the local mean ¯ow and wall-normal directions. At downstream stations, the contributions to the turbulent shear stress from quadrant 4 (sweeps) are predominant in the region near the wall. It is thus revealed that strong ejections are suppressed by the eects of increased three-dimensionality.