AbstractOver the past two decades there have been great advances in the understanding of depression and in the development of pharmacological agents and psychosocial treatments that have demonstrated efficacy in the treatment of this common and disabling illness. Unfortunately, this knowledge and evidence is not consistently translated into actual treatment, and depression remains undiagnosed in a large percentage of patients, and when it is accurately diagnosed, it often is suboptimally treated.The frequent failure to properly diagnose depression may be due to the continuing stigma of mental illness, the persistence of the biomedical, rather than the biopsychosocial, paradigm of illness and treatment, educational issues and the time constraints in the typical medical practice. The suboptimal treatment may be due to all of these issues plus the difficulty in changing physician behaviours even when there exists much evidence that would seem to dictate such a change. The development of a criteria‐based nomenclature and the subsequent development and dissemination of evidence‐based practice guidelines addresses some of these issues. Copyright © 2001 John Wiley & Sons, Ltd.