Up to 50% of patients seen in primary care have mental health problems, the severity and duration of their problems often being similar to those of individuals seen in the specialized sector. This article describes the reasons, advantages, and challenges of collaborative or shared care between primary and mental health teams, which are similar to those of consultation-liaison psychiatry. In both settings, clinicians deal with the complex interrelationships between medical and psychiatric disorders. Although initial models emphasized collaboration between family physicians, psychiatrists, and nurses, collaborative care has expanded to involve patients, psychologists, social workers, occupational therapists, pharmacists, and other providers. Several factors are associated with favorable patient outcomes. These include delivery of interventions in primary care settings by providers who have met face-to-face and/or have pre-existing clinical relationships. In the case of depression, good outcomes are particularly associated with approaches that combined collaborative care with treatment guidelines and systematic follow-up, especially for those with more severe illness. Family physicians with access to collaborative care also report greater knowledge, skills, and comfort in managing psychiatric disorders, even after controlling for possible confounders such as demographics and interest in psychiatry. Perceived medico-legal barriers to collaborative care can be addressed by adequate personal professional liability protection on the part of each practitioner, and ensuring that other health care professionals with whom they work collaboratively are similarly covered.