The Hall effect in trigonal selenium single crystals has been measured by a dc method. The measurements give a carrier concentration of 0.5×1015cm−3at room temperature and 1015cm−3at 100°K. The conductivity is ofptype within the entire temperature range. By illumination with extrinsic light the carrier concentration has to a certain extent turned out to be independent of the intensity of light. The mobility calculated from a barrier model is about 260 cm2/V sec at room temperature in the direction of thecaxis. The value is considerably higher than earlier reported values.