Many important issues in modern Chinese history are crucially affected by the magnitude and pattern of economic growth up to 1937. Despite the work of John Key Chang and more recently Thomas Rawski, however, we still know all too little about the quantitative aspects of that growth. All scholars of the period are greatly indebtedto Chang's pioneering and indispensame work on industrial production but, as he himself points out, his index remains tentative and exploratory. Although the compilation of a definitive new index will eventually depend on work by scholars in China, to my knowledge this has not yet got under way. Wherever compiled, any index of industrial output as a whole, or even of national income, will have to be based on better series for individual industries. In such a context, this research note builds on Chang's work by offering a revision of the output series for one very important and rapidly growing industry in pre-1937 China, the electric power industry.