Low back pain is an enormous and important clinical and public health problem. Although admittedly common, its epidemiology is difficult to determine precisely. There is a problem of definition and classification. For example, the results of a survey will depend on definitions of the severity of pain, period of pain, medical attention required, disability caused by, etc. Further, there is a measurement problem since back pain can exist without objective evidence and pain cannot be directly measured. In addition, poor recall, influence of legal, social, psychological and work-related factors, and the intermittent nature of back pain creates validity and reliability problems. Thus, the data are to be viewed as an approximation.Background-where we stand today