The aim of this Editorial is to discuss depression as an important disorder for public health. The literature regarding epidemiology, consequences, adequacy of service delivery and prevention of depression is reviewed. Depression is a common disorder with high lifetime rates, particularly in women, and those experiencing social adversity. It is a major cause of disability, and causes death both by suicide and due to raised rates of physical disorders. Many cases are undiagnosed and treatment is often inadequate. Primary prevention is not yet easily feasible but secondary prevention by earlier recognition, public and professional education, can produce benefits. There is a need for public health programmes aimed at improving recognition, treatment, and reducing consequences.