Several treatment principles for the reduction of chronic low back pain associated disability have been postulated. To examine whether a combination of a physical training and an operant-behavioral graded activity with problem solving training is more effective than either alone in the long-term, a cluster randomized controlled trial was conducted. In total 172 patients, 18-65 years of age, with chronic disabling non-specific low back pain referred for rehabilitation treatment, were randomized in clusters of four consecutive patients to 10 weeks of aerobic training and muscle strengthening of back extensors (active physical treatment; APT), 10 weeks of gradual assumption of patient relevant activities based on operant-behavioral principles and problem solving training (graded activity plus problem solving training; GAP), or APT combined with GAP (combination treatment; CT). The primary outcome was the Roland Disability Questionnaire adjusted for centre of treatment, cluster, and baseline scores. Secondary outcomes were patients' main complaints, pain intensity, self-perceived improvement, depression and six physical performance tasks. During the one-year follow-up, there were no significant differences between each single treatment and the combination treatment on the primary outcome, the Roland Disability Questionnaire. Among multiple other comparisons, only one significant difference emerged, with GAP and APT showing higher self-perceived improvement than CT. We conclude that the combination treatment integrating physical, graded activity with problem solving training is not a better treatment option for patients with chronic low back pain.