This thesis presents measurements of the three-dimensional flow due to the horseshoe vortex formed at the junction of a flat wall and the leading edge of a Rankine half body. The half body is located between the parallel end walls of a duct to model the situation in turbomachinery where struts and vanes, which generate performance losses due to horseshoe vortices and other secondary flow mechanisms, extend over the total flow passage height. The boundary layer on the duct end wall is artificially thickened to produce a large horseshoe vortex. Flow measurements are presented showing the inlet flow and the three-dimensional flow just downstream of the leading edge of the body. Sufficient data is presented to provide a means for testing the validity of three-dimensional viscous flow calculations. A three-dimensional flow measurement technique using a single slanted hotwire anemometer is evaluated. The hotwire anemometer measurements are compared with measurements of the same flow made with a five-hole pressure probe. A two-dimensional laminar and turbulent boundary layer analysis is performed at mid-height on the body. / M.S.