Low back pain (LBP) is a highly prevalent and costly cause of disability. In spite of a large amount of research in this field, there is still controversy about which factors are more important to determine chronicity in low back pain. Recent results have shown that LBP becomes a chronic condition mainly because of the relationship between psychosocial factors and pain. This relationship would explain the resistance of chronic LBP to classical medical treatment, which results in absenteeism and high economical costs. In this study we review recent results, including our own, that elucidate the contribution of psychosocial factors to chronic LBP. A biopsychosocial approach to these patients is highly recommended (Rev Méd Chile 2002; 130: 1411-8)