The magnetic barrier at Venus is a region within which the magnetic pressure dominates all other pressure contributions. The barrier is formed in the inner region of the dayside magnetosheath to transfer solar wind momentum flux to the ionoshpere. Passes through the dayside magnetosheath and ionopause with Pioneer Venus have allowed us to probe the magnetic barrier directly. These passes have been used to construct altitude profiles of the barrier. Here we define the ionopause as the lower boundary of the barrier. The upper boundary is defined as the altitude where the magnetosheath magnetic pressure is equal to half of the upstream solar wind dynamic pressure corrected by the boundary normal angle. The magnetic barrier is strongest at the subsolar point and weakens as expected with increasing solar zenith angle. The existence of a north-south asymmetry in the barrier strength is also demonstrated. The magnetic barrier is about 200 km thick at the subsolar point and 800 km thick at the terminator which is comparable with the so-called ''mantle.'' We find that the magnetic barrier transfers most of the solar wind dynamic pressure to the ionsophere via the enhanced magnetic pressure. The convected field gasdynamic model is found to predict the correct bow shock location if the magnetic barrier is treated as the obstacle. ¿ American Geophysical Union 1991