The present study examined the contribution of physical pathology, pain-related fear and catastrophizing cognitions to pain intensity and disability in 100 patients with non-specific low back pain. Self-report instruments were completed as part of the intake procedure of patients, while physical pathology was quantified from medical charts using the MEDICS procedure. Results of the multiple regression analyses, adjusted for relevant demographic variables, pain intensity and pain duration, indicated that physical pathology was associated with pain intensity, but not with self-reported physical disability. Disability showed the strongest association with pain intensity. However, pain-related fear and catastrophizing contributed 4-10% additional explained variance to the regression models for pain intensity and disability. Thus, this study confirms the relationship between biological and psychological variables in determining the severity of low back pain complaints, and underscores the necessity for a multidisciplinary approach to diagnostics and intervention.