In South Africa, particularly on the Witwatersrand, increasing quantities of crusher sand are being used in concrete and mortar. An investigation has been carried out to determine the concrete- and mortar-making properties of crusher sand derived from crushing of Witwatersrand quartzite at two different crushing plants. At one plant the crusher sand was washed as a routine operation. The results indicate that there are no valid reasons why washed crusher sand in particular should not be used in concrete and mortar. Much could, however, be done to improve the grading and shape of material at present being sold as crusher sand. It is concluded that crusher sand, derived from the crushing of Witwatersrand quartzite and manufactured under controlled conditions, warrants consideration for use in concrete and mortar.