One of the means of generating terahertz (THz, 1012 Hz) frequency radiation is through the bulk second-order nonlinear effect of optical rectification. Optical rectification occurs if high-intensity light is directed onto an electrooptic material such as ZnTe. If the excitation beam contains components of two or more frequencies then difference-frequency mixing, also known as optical rectification, may take place. Depending on the spectrum of the excitation beam, the resulting frequency may be in the THz range. While this phenomenon has been known for some time, and has been studied in various zinc blende crystals, attention does not seem to have been paid to the precise relationship between the s and p polarised components of the emitted radiation. Moreover, only crystals with (100), (110) or (111) faces appear to have been investigated to date. We extend the previous work by undertaking a careful analysis of the THz radiation emitted by (110) ZnTe as a function of the angle of rotation of the crystal about its surface normal, and by investigating the THz radiation emitted from crystals of other orientations, such as (311).