What is the role of treating physicians and therapists with respect to return-to-work when they are treating with chronic LBP? Do workers with ergonomic interventions return to work more quickly for a long-lasting period compared to workers without these interventions? We are going to conduct a study on the effectiveness of four treatment option, what are important aspects in the design of this study to answer the research questions? How is the workplace intervention and its implementation evaluated by LBP-patients and their occupational health professionals. These and other questions are answered in this thesis, which puts together the current evidence, draws lessons to be learnt from experiences, and gives recommendations for reviewing clinical and occupational guidelines and for new research to be conducted.