This paper examines the causes of the differences in the average energy intensity for the manufacturing sector for ten countries of the Organization for Economic Cooperation and Development (OECD), The industrial composition of the manufacturing sector cannot explain the intensity differences, The intercountry difference in trade patterns is also a minor factor, The major reason for the difference appears to be the nature of processing carried out in each country, The pulp and paper industry was selected, as an example, for an in-depth analysis, Countries such as Canada and the Scandinavian nations, who concentrate on primary processing (pulp and paper production), have a higher energy intensity for this industry than those countries who focus mainly on secondary production, such as paper products and printing, The main conclusion drawn from this result is that an international comparison of energy intensity, at the aggregate level, produces misleading conclusions with respect to energy efficiency and the quality of technology used in a particular country, An analysis at the sub-industry level should be undertaken to gain an insight into these issues.