Intervention effectiveness research (IER) and the organization of work are two priorities of the US National Occupational Research Agenda (NORA). In addition, the organization of work is considered a strong contributor to the development of musculoskeletal disorders, a third NORA priority. Few studies have been conducted to date to evaluate the impact of interventions aimed at concretely reducing adverse work organization factors and the comprehensive range of their health impact The objective of the study is to evaluate the benefits of interventions aimed at reducing adverse work organization factors (high psychological demands, low control, poor social support, and effort-reward imbalance) and their health impact, measured by ambulatory blood pressure, musculoskeletal disorders, mental health problems and certified sick leave.The study has the following specific aims: 1) To produce knowledge that will foster the development of well-adapted interventions designed to concretely reduce adverse work organization factors. This will be achieved through the combined use of quantitative evaluation of the importance of adverse work organization factors and health problems (prior risk evaluation) and qualitative methods aimed at using worker's and manager's knowledge of real work situations, namely focus groups with workers and follow-up with managers. 2) To systematically document how the intervention is carried out. Intervention refers to organizational changes implemented to concretely reduce the four targeted adverse work organization factors. The nature and intensity of these organizational changes will be assessed and information on those contextual elements that hinder or facilitate the desired changes will be collected through interviews with top management, a work organization changes log, and follow-up of focus groups with employees. 3) To measure the extent to which the intervention reduced the prevalence of adverse work organization factors and the level of health outcomes. Effectiveness of the intervention will be evaluated with a quasi-experimental design including a control group and pre and post-measures. Certified sick leave will be collected for two years preceding the intervention and for the following three years. All of these measures will be monitored in all workers belonging to the intervention group (N=1700) and in all workers belonging to a suitable comparable workplace (N=1000) before, at 18 months and at 36 months after the intervention. This study will provide solid new findings that could be used to prevent cardiovascular disease, musculoskeletal disorders and mental health problems, the most frequent, costly and debilitating health problems in the working age population.