Employing the stochastic frontier approach, this paper investigates cost X-efficiency in China's banking sector over the period 1985-2002. The objective is to assess whether different ownership types and banking reforms affect X-efficiency. A two-stage regression model is estimated to identify the significant variables influencing X-efficiency. Overall, the results show that banks are operating 40-60% below the X-efficiency frontier. On average, the joint-stock banks are found to be more X-efficient than the state-owned commercial banks, but individual scores present a far more complex picture. It appears that X-efficiency was higher during the first phase of bank reform. Recent policies aimed at increased privatisation, greater foreign bank participation, and liberalised interest rates should help to improve the cost X-efficiency of China's banks.