The diffraction of SH waves by a wedge-shaped elastic medium is studied. Macdonald's (1902) solution is derived and applied to calculate the field in the wedge's surface on and near the vertex. It is found that the motion at the vertex, relative to the free space amplitude, is given by 2/v, where vπ = internal angle of the wedge. In some cases, values much larger than 2/v were found on the sides. Both frequency and time domain results are given.