This study critically reviewed current conceptualizations of occupational disability resulting from low back pain (LBP). It proposes a new classification system for back pain built on a phase-model of disability. The goal was to develop a classification system that overcomes the shortcomings of existing classification schemes and is useful for interdisciplinary research, prevention, treatment, and rehabilitation. Attempts to study and prevent disability resulting from LBP have been hampered by the use of inadequate classifications of LBP. Current classifications of LBP were critically reviewed, and criteria for a useful classification system are described. The disabling process is organized in eight consecutive phases determined by the presence and duration of work disability. The proposed eight-phase classification is based primarily on the presence and duration of work-disability rather than on clinical categories. It takes into account the developmental and social character of disability. The simplicity, reliability, and expandability of the model allow for its interdisciplinary use in research and intervention. The prevention of disabling back pain requires an interdisciplinary approach. For this purpose, other than purely biomedical classifications of LBP are needed. The authors propose an eight-phase classification system primarily based on the duration of work disability and that takes into account other biomedical, developmental, and social characteristics of work-disability resulting from LBP.