Introduction: To identify different types of work organization among workers of the Pays-de-la-Loire region (France) and to compare their impact on the prevalence of MSD. Methods: A total of 3710 workers of a French region were randomly included in 2002-2005. Occupational data were assessed by a self-administered questionnaire. Sixteen organizational variables were studied: shiftwork (rotating or non-rotating), job rotation, eight variables measuring the decision latitude, repetitiveness of tasks, five variables measuring the work pace dependent on: automatic rate, quantified targets, permanent controls or surveillance, colleagues' work and demand of customers. Workers without missing values were studied (n=3304). Two methods were used to classify workers according to the work organization: 1) multiple correspondence factor analysis (MCA) and hierarchical cluster analysis (HCA) and 2) clustering of variables and HCA. Results: The first method identified five classes, characterized by an overrepresentation of: - First class (25% of workers): job rotation, decision latitude and work pace dependent on demand of customers - Second class (22%): decision latitude, work pace dependent on: quantified targets, permanent controls or surveillance, colleagues' work and demand of customers. - Third class (24%): non rotating shiftwork and decision latitude - Fourth class (15%): non rotating shiftwork and repetitiveness of tasks - Fifth class (14%): shiftwork (rotating or non-rotating), job rotation, repetitiveness of tasks, work pace dependent on: automatic rate, quantified targets, permanent controls or surveillance and colleagues' work. The prevalence of MSD in the different classes was 10%, 11%, 11%, 14% and 18%, respectively (p<0.001). The prevalence of rotator cuff syndrome, the most prevalent of MSD, in the different classes was 5%, 6%, 7%, 8% and 11%, respectively (p<0.01). Discussion: Results of the second method of classification and its comparison with the first method of classification and its relationship with the prevalence of MSD will be presented at the conference.