Objective: To determine whether a psychiatric-psychosomatic consultation can identify unmet treatment needs and improve treatment of patients with mental disorders in general practice. Methods: In 40 primary care practices, 307 consecutive primary patients who met criteria for chronic mental disorders were assessed by a psychiatric-psychosomatic consultant. After random assignment, general practitioners (GPs) were informed for half of the patients about the results of the assessment and received recommendations on how to improve treatment. Changes in treatment and patient status were reevaluated after 6 months. Results: Patients were mostly having depression, adjustment, or anxiety disorders, with 28.8% on sick leave. Contact with their respective GPs was longer than a year in 77.2% of cases. Patients had already received pharmacotherapy (60.9%), psychotherapeutic counseling by GPs themselves (27.7%), psychotherapy by specialists (73.9%), psychiatric outpatient care (57%), inpatient psychiatric treatment (12.1%), inpatient psychosomatic rehabilitation (ie, specialized behavioral medicine facilities for patients with work problems; 41.4%), and a broad spectrum of other diagnostic and therapeutic measures. Newly recommended interventions included leisure activities (42%), a new specialist psychotherapy (37.5%), or inpatient psychosomatic treatment (15.3%). Most recommendations were agreed upon by the GP. Nevertheless, there was only a limited increase in therapeutic actions 6 months later, and no statistically significant improvement in the status of patients. Conclusion: General practitioners undertake a broad spectrum of therapeutic interventions in patients with chronic mental disorders. According to our results, additional psychiatric-psychosomatic consultations can intensify treatment but does not significantly change the general course of chronic mental disorders.