Summary This project seeks to determine the factors related to the meaning of work that have an impact on mental health in the workplace and organizational commitment. The expected results are used to verify the relationships between the factors of meaning of work, mental health and organizational commitment and recommend actions to correct or improve the factors that affect the meaning of work. The following hypotheses were tested: The following work characteristics are positively correlated to each other: social purpose, moral correctness, learning and development opportunities, autonomy, recognition and positive relationships. The 6 characteristics are positively correlated to the meaning of work. The meaning of work positively influences psychological well-being. The meaning of work negatively influences psychological distress. The meaning of work positively influences affective organizational commitment. The research presented here was conducted in 4 different organizations: a Hospital Centre (2001-2003; 262 subjects), a Health and Social Services Centre (CSSS) (2006-2007; 955 subjects), an Agricultural Research Centre (2005-2007; 101 subjects) and an Engineering Firm (2006-2007; 305 subjects). Except for the Engineering Firm, the other organizations included unions. This is applied research, which involves several advantages, but also has to overcome several difficulties. Applied research has the advantage of improving the understanding of specific and concrete problems, and determining realistic solutions to these problems. A Consultative Committee was formed upon initiation of the project in each organization to assume the functions of consultation and liaison between the research team and the personnel. This was a participatory survey involving three stages: pre-survey, survey and the feedback meeting. Except for the first survey, which was conducted in a Hospital Centre, the survey questionnaire was divided into two parts, with the second administered three weeks after the first. This procedure has the advantage of controlling the effect of common variance between the independent and dependent variables. The first part of the questionnaire contains questions and scales essentially evaluating work, working conditions and interpersonal relations among employees. The second part makes it possible to evaluate organizational commitment and involvement, psychological well-being, psychological distress, and perception of physical health. The first part of the questionnaire contains the following scales and questions: Representations of work (15 statements, 6 points, MOW International Research Team, 1987) Characteristics of meaningful work (26 statements, 6 points, Morin & Dassa, in preparation) Physical, mental and emotional workload (12 statements, 6 points, Morin, 2002) Description of the work schedule, its impacts on sleep and work-life balance (SSI, Barton & al. 1993) • Recognition (effort and reward balance, 10 statements, 6 points, Siegriest, 1996) Perception of justice (18 statements, 6 points, Moorman, 1991) Perception of the relationship with an immediate superior (LMX) (7 statements, 5 points, Graen & Uhl-Bien, 1995) • Supervisory behaviour (40 statements, 5 points, Rousseau & Aubé, 2005) The meaning of work (6 statements, 6 points, May, Gilson & Harter, 2004) Questions allowing information gathering on the respondent and his/her job. The second part includes the following scales and questions: Empowered behaviours (19 statements, 10 points, Boudrias & Savoie, 2006) • Meaning of work (6 statements, 6 points, May, Gilson & Harter, 2004) Forms of organizational commitment (18 statements, 6 points, Meyer & Allen, 1993) Significant life events (20 statements, yes, no, not applicable, Dohrenwend, 1973) For the Hospital Centre and the Agricultural Research Centre The Psychiatric Symptoms Index - PSI (14 statements, 4 points, Ilfeld, 1976) For the CSSS and the Engineering Firm The EMMDP indicator of psychological distress (23 statements, 5 points, Massé & al., 1998) The EMMBÉP indicator of psychological well-being (25 statements, 5 points, Massé & al., 1998) General health perception - GHP (5 statements, 6 points, Bjorner & Kristensen, 1996) Following correlation analyses performed on the 4 data sets, all these hypotheses were retained. The linear regression analyses pinpointed the determining effects of recognition and the meaning of work, both on mental health and affective commitment, as well as the mediating effect of the meaning of work in the relationship among the characteristics of work, mental health and affective commitment. It is interesting to observe that social purpose and learning and development opportunities are two factors that have a significant effect on the meaning of work. Also, we must mention the effect of the “moral correctness” factor on employees’ affective commitment. Based on these results, a theoretical model is proposed to orient future research in this field.