Southern hemisphere and South African regional air temperature anomalies for the period 1860--1996 are compared to borehole-derived surface rock-temperature anomalies to assess the extent to which surface rock temperatures reflect possible global warming in South Africa. The warming of the southern hemisphere since the mid-nineteenth century is evident in the regional air temperatures for South Africa. Following a temperature increase to a maximum in the 1920s, the climate cooled until strong warming recommenced in the mid 1970s. Highest temperatures have been experienced in the 1990s. Borehole-derived surface rock temperatures followed a similar pattern, but with a lag of a few decades in the case of the 1920s maximum. The overall warming trend is clearly evident in the rock temperatures. Despite uncertainties in the different data sets, an encouraging degree of agreement exists between the increase in rock temperatures during the twentieth century, the corresponding regional South African air temperature increase and the southern hemisphere counterpart. ¿ 1998 American Geophysical Union