In this paper, we present an in-depth decomposition analysis of trends in CO2 emissions in the iron and steel industry using physical indicators. Physical indicators allow a detailed analysis of intra-sectoral trends, in contrast to the mostly used monetary indicators. Detailed decomposition analysis makes it possible to link developments in energy intensity to technology change and (indirectly) to policy. We present an analysis for the iron and steel industry in seven countries, i.e. Brazil, China, India (developing countries), Mexico and South Korea (newly industrialized countries) and the United States (industrialized country). We found substantial differences in energy efficiency among these countries. In most countries the increased (or decreased) production was the main contributor to changes in CO2 emissions, while energy-efficiency was the main factor reducing emission intensities of steel production in almost all countries. Changes in power generation contributed to a reduction of specific emissions in the case of South Korea only.