Under pressure from donor agencies such as the World Bank, a number of developing countries have experimented with the privatisation of water services. This study reviews the existing econometric evidence on the effects of water privatisation in developing economies before presenting new results using statistical, data envelopment analysis (DEA) and stochastic cost frontier techniques and data from Africa. The study finds evidence of better performance in private utilities compared to state-owned utilities according to the statistical and DEA performance measures. But no statistically significant cost differences were discovered between private and public suppliers in the stochastic cost frontier analysis. The paper then considers reasons why water privatisation may prove problematic in lower-income economies, identifying the technology of water provision and nature of the product, transaction costs and possible regulatory weaknesses. However, a second-stage cost function analysis introducing a regulatory variable produced statistically insignificant results.