Low back pain and fibromyalgia represent two of the most common disorders in developed countries. On the whole, up to 75% of the general population has, at some time, suffered from low back pain. A percentage ranging between 5 and 10% of them develops a chronic illness. In most countries, the incidence rate per year of low back pain is 5%. Most low back pain episodes occur between the ages of 25 and 55 years. Most studies have not found any clear influence between genders and frequency of low back pain. There is a relationship between low back pain and occupation, with those who have physically demanding jobs being more at risk. As regards fibromyalgia, the prevalence rates range between 6 and 20%, with a higher frequency among females and between the ages of 25 and 55 years. The direct and indirect costs of low back pain approach $24 billion per year in the U.S. It is in view of its high prevalence among populations of developed countries, of its heavy psychosocial and financial implications, and of the burden imposed on health services, that low back pain represents a severe public health problem.