A number of studies carried out in other countries have shown the existence of negative correlations between cardiovascular disease mortality and the hardness of water supplies. A study here showed negative correlation (P less than 0.10) between cardiovascular disease mortality for the South African urban white population and total water hardness (equivalent calcium carbonate mg/l). Negative correlations were also found to exist with the hardness-associated factors potassium (P less than 0.05), sulphate (P less than 0.05) and chloride (P less than 0.05) and manganese (P less than 0.10). The results are described in terms of existing studies and a number of local problems have been identified and discussed.