Recent studies have indicated the pernicious nature of dysthymia; its low-grade chronicity probably contributes most to the problem of under-treatment and misdiagnosis. A high prevalence of morbidity and comorbidity is associated with dysthymia: major depression, alcoholism, anxiety and personality disorders are present in the vast majority of sufferers. It is also very unusual for people with dysthymia to not develop superimposed episodes of major depressive disorder, resulting in a longer time to recover and high rates of recurrence and chronicity. Approximately 3.1% of the population have dysthymia including children and adolescents who, like adults, exhibit a higher risk for new episodes of depressive illness if they have this disorder. Children and adolescents with depressive illnesses have higher rates of scholastic failure and school-related problems. Dysthymia can affect every aspect of a person's quality of life including relationships with significant others, earning potential and, most importantly, mental and physical well-being. Available data is not yet sufficient to differentiate dysthymia as a disease entity from the other depressive disorders such as major depression or double depression, or to conclude to what extent dysthymia should be thought of as a personality disorder. However, the DSM-IV Mood Disorders Field Trial results help identify new criteria for the DSM-IV Appendix. The relationship between dysthymic disorder and major depression needs more definition, especially in regard to course and severity, so that an accurate diagnosis can lead to expeditious and appropriate treatment.