The study investigates the accuracy of mass valuations for the purpose of levying assessment rates (land taxes) in one metropolitan council of South Africa. The sample frame is the Valuation Roll for greater Johannesburg, which was prepared in January 2001 and is still current. The sample frame contains 509705 records. Those properties that were sold in the period immediately preceding the valuation date and in the period immediately following the valuation date are selected and actual selling prices are compared with the valuation. Conclusions on accuracy of the Johannesburg Valuation Roll are drawn.