OBJECTIVE To document the management of mental health problems (MHPs) by general practitioners. DESIGN A mixed-method study consisting of a self-administered questionnaire and qualitative interviews. An analysis was also performed of Régie de l'assurance maladie du Québec administrative data on medical procedures. SETTING Quebec. PARTICIPANTS Overall, 1415 general practitioners from different practice settings were invited to complete a questionnaire; 970 general practitioners were contacted. A subgroup of 60 general practitioners were contacted to participate in interviews. MAIN OUTCOME MEASURES The annual frequency of consultations over MHPs, either common (CMHPs) or serious (SMHPs), clinical practices, collaborative practices, factors that either support or interfere with the management of MHPs, and recommendations for improving the health care system. RESULTS The response rate was 41% (n = 398 general practitioners) for the survey and 63% (n = 60) for the interviews. Approximately 25% of visits to general practitioners are related to MHPs. Nearly all general practitioners manage CMHPs and believed themselves competent to do so; however, the reverse is true for the management of SMHPs. Nearly 20% of patients with CMHPs are referred (mainly to psychosocial professionals), whereas nearly 75% of patients with SMHPs are referred (mostly to psychiatrists and emergency departments). More than 50% of general practitioners say that they do not have any contact with resources in the mental health field. Numerous factors influence the management of MHPs: patients' profiles (the complexity of the MHP, concomitant disorders); individual characteristics of the general practitioner (informal network, training); the professional culture (working in isolation, formal clinical mechanisms); the institutional setting (multidisciplinarity, staff or consultant); organization of services (resources, formal coordination); and environment (policies). CONCLUSION The key role played by general practitioners and their support of the management of MHPs were evident, especially for CMHPs. For more optimal management of primary mental health care, multicomponent strategies, such as shared care, should be used more often.