Rapid population growth and industrialisation within metropolitan areas is a potential danger. The control of pollution in sensitive areas depends on the definition End control of sources. In this paper, results of the industrial source inventory and characterization study in the Istanbul watershed areas have been summarized. Emphasis has been given on industrial waste load assessment approaches and the methodology followed in the Istanbul watersheds has been given in detail and illustrated. Industrial loads are presented by industrial subcategory. Results of the study are evaluated and discussed. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.