Local mass transfer from the surface of a wall-mounted cube is studied using the naphthalene sublimation technique. The streakline pattern on each face of the cube is visualized using the oil-graphite method. A horseshoe vortex system near the endwall, in conjunction with the separated shear layers initiated at sharp edges, determines the transport characteristics around the cube. As a direct influence of the flow field, the local mass transfer distributions reflect features of three-dimensional flow separation that are significantly different from their two-dimensional counterparts existing in the midsection of a long prism. According to several previous studies, average mass transfer over the rear surface of a square prism without end effects is the highest among all surfaces. However, it is the lowest for the present case with a wall-mounted cube. The cube side wall has the highest average mass transfer overall. This is a result of the elevated local mass transfer existing in the lower portion of the surface, near which a horseshoe vortex system prevails. In addition to local data, correlations of average Sherwood number with Reynolds number are also presented for various surfaces.