A detailed understanding of material stocks in use is essential for anticipating future scrap availability, identifying critical drivers for material use, and developing strategies for resource efficiency. Here, we present a bottom-up assessment of iron and steel stocks in use in urban and rural China for the years 2000 and 2010, including >250 subcategories of products and components, and grouping them into five main end-use categories (i.e., buildings, infrastructure, domestic appliances, machinery, and transport equipment). The uncertainty range of the steel content per type of stock, a determinant of the accuracy and usefulness of the stock accounting, is probed by multiple means, including sample analysis. Important findings are that (1) iron and steel stocks in China have climbed to 2.4 tonnes/capita (t/cap) in 2010, up from 0.9 t/cap in 2000. The use of reinforced concrete in construction of the urban built environment was the major driver for stock growth; (2) a rural-urban difference was uncovered, with rural iron and steel stocks of approximately 1.1 t/cap and the urban iron and steel stocks of approximately 3.7 t/cap in 2010. Both are, nevertheless, far below the level of 10 to 16 t/cap observed in highly industrialized and urbanized countries. For this reason, further stock increase is foreseeable as urbanization and industrialization proceeds and quality of life improves; (3) nearly half of the steel stocks were embedded in concrete structures, and 23% were located in the countryside. Only a fraction of these stocks are currently recovered at end of life