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In semi-arid and arid magisterial (administrative) districts (n = 45) in the Cape Province, South Africa, there has been a mean 44·4 ± 14·6% (S.D.) reduction in the stocking rates of domestic livestock over the period 1911-81. In five savanna districts there has been a mean 36·8 ± 8·5% increase in stocking rate. For all districts during the period 1911-30 the mean stocking rate was 12·5 ± 8·6 large stock units/100 ha, and for 1971-81 the mean rate was 8·4 ± 7·7 LSU/100 ha (one bovid weighing 420 KG = 1 LSU). The reduction in stocking rate differs significantly between biomes and shows a general trend towards being greater in the more arid districts. The reduction is significantly greater in the succulent Karoo where seven of eight districts have experienced stocking rate reductions > 50%. Districts with a rainfall variability index > 4·0 (i.e. with lowest recorded rain only 25% or less of highest recorded rain) show a significant trend towards larger reductions in stocking rate than do all the other districts. Reductions in stocking rate, however, are not significantly correlated with the index of rainfall variability or with an index of drought, suggesting that changes in stocking rate are not influenced only by higher probabilities of drought. Past and present stocking rates are significantly correlated with mean annual rainfall in the eastern Karoo, central Karoo, succulent Karoo and Savanna districts. The total number of stock-water points in each district in all biomes increased over time. In Gordonia, Kuruman, Mafeking, Taung and Vryburg, where stocking rates have increased, they are positively correlated with stock-water points, but in all other districts, this relationship is negatively correlated. We conclude that the current livestock stocking rate in the semi-arid and arid rangelands of the Cape Province is unrelated to market forces or state policy but is determined by utilizable primary productivity of rangelands. This study provides evidence that the production potential of drylands has decreased markedly in semi-arid and arid rangelands throughout the Savanna, Nama-Karoo and succulent-Karoo biomes of the Cape Province.