This paper presents a new data set on the number of enterprises, employees, gross output and value added in manufacturing by size category. The figures are obtained from censuses of manufactures and industrial surveys for three years (one year in the 1960s, one year in the 1970s, and one year in the late 1980s or 1990) and five OECD countries (France, Germany, Japan, the United Kingdom and the United States). There are five or six size categories, which are established on the basis of the number of employees per enterprise or establishment. The level of industry disaggregation is according to that in the STAN database. The paper discusses the basic sources and presents the complete data set. It also contains a brief analysis of average firm size, relative productivity levels per size category and concentration ratios ...