The Compatible Trade and Production data base (COMTAP) consists of annual statistics on production, imports and exports of manufactured goods. The key feature of this data base is that both the production and trade statistics are classified according to the same nomenclature, namely, the International Standard Industrial Classification (ISIC). The conversion of both trade and production statistics to the ISIC is approximate because there is usually no direct correspondence between the ISIC and the classification in which the trade and production data are reported to the OECD. This report describes the contents of COMTAP , some of the analytic uses to which it can be put, and the problems encountered in setting up the COMTAP data base. Finally, some examples are given of how the data base can be used to calculate "market penetration ratios" for 13 OECD countries over the period 1970 to 1983. The annexes present some of the COMTAP data in summary form ...