An experimental investigation of the zero pressure gradient turbulent boundary layer along a 90 degree streamwise corner is reported. Turbulent non-turbulent conditional sampling measurements in the outer intermittent region of the boundary layer as well as a comprehensive set of conventional measurements were made in a cross section at 1.7 m down stream from the leading edge. The results of a turbulent zone averaged secondary velocity field indicate a set of closed streamwise vortex patterns near the corner, as in the conventional measurements. A large difference was found in the outer part of the boundary layer, where the turbulent zone averaged secondary flow moves from the wall to the free stream direction. On the contrary, the non-turbulent zone averaged counterpart moves from the free stream to the wall and which includes almost no streamwise vorticity, indicating that the secondary flow of the second kind is generated only when the flow is turbulent.