Manual material handling (MMH) tasks, the leading cause of low back disorders (LBDs). are still extensively used in industry in spite of the advanced technology. Classification of industrial jobs related to LBD risks has great significance in preventing injuries and designing workplaces. In this article. industrial jobs have been classified into two categories. low risk and high risk using ant colony optimization (ACO). ACO classification (ACOCLASS) has obtained better results than Studies that Used the same experimental data. Ergonomic interventions can be done by means of obtained classification schema for future reductions in low back injuries. (C) 2008 Wiley Periodicals. Inc.