The important Middle Pleistocene fauna1 site of Cornelia, Orange Free State, South Africa comprises a major fossiliferous horizon that overlies an archaeological level with late Acheulian artifacts. The geological context and the archaeological and palaeontological significance at this site are described in a recent monograph on Cornelia by Butzer et al. (1974). This paper provides a uranium-series date on a molar of Equus cf. burchelli from the major fossil level (Member 1, bed 6) of the Cornelia Formation, Dating bones that are associated with archaeological materials has been attempted previously (Szabo et al., 1969; Howell et al., 1972; Szabo et al., 1973; Sakanoue & Yoshioka, 1974; Szabo & Collins, 1975). The dates are derived by measuring 230Th and 231Pa isotopes that are produced through time by their radioactive parents 234U and 235U, respectively. The requirements for reliable dating are the following: the sample initially takes up uranium, but no thorium or protactinium; this occurs in a short time early in its history; and the sample remains closed to gain or loss of the nuclides of uranium and their long-lived decay products 230Th and 231Pa. The uranium concentration is low in modern bones, less than 0.1 ppm. In contrast, uranium contents in fossil bones may vary from l-1000 ppm; thus a measurable time lag is expected for the uptake of uranium. It appears that uranium, that is readily soluble in ground waters, enters the bone after the death of the animal and it is reduced and precipitated by the decaying organic matter within the fossil. This process of uranium emplacement continues until all active organic matter is decomposed. Szabo (1974) has reported that the average time lag for uranium uptake in eight samples from varied geological environments is about 3000 years when compared with radiocarbon dates on shells, bones and other dateable materials found in close association with the uraniumseries dated bones. The method presently available for scrutinizing the closed system assumption is to obtain both 230Th and 231Pa ages for each fossil bone. One may place confidence in single sample dating only if these independent ages are concordant. Very few uranium-series dating studies that yield apparently reliable concordant 230Th and 231Pa dates have been tested against other methods in the age range greater than the upper range of radiocarbon dating, about 30,000 years. One date for an Acheulian