Patients with clinically significant symptoms of depression who do not meet the criteria for major depressive disorder or dysthymic disorder are considered to have subthreshold depression. According to DSM-IV, such patients should be diagnosed with depressive disorder not otherwise specified (NOS) if the development of the symptoms is not attributable to a stressful event or with adjustment disorder if the symptoms follow a stressor. Research on the treatment of subthreshold depression rarely addresses the distinction between depressive disorder NOS and adjustment disorder. In the present report from the Rhode Island Methods to Improve Diagnostic Assessment and Services (MIDAS) project, we examined the validity of this distinction.From December 1995 to June 2011, 3,400 psychiatric patients presenting to the Rhode Island Hospital outpatient practice were evaluated with semistructured diagnostic interviews for DSM-IV Axis I and Axis II disorders and measures of psychosocial morbidity.Slightly less than 10% (n = 300) of the 3,400 patients were diagnosed with depressive disorder NOS or adjustment disorder with depressed mood. The patients with depressive disorder NOS were significantly more often diagnosed with social phobia (P < .05) and a personality disorder (P < .01). The patients with depressive disorder NOS reported more anhedonia, increased appetite, increased sleep, and indecisiveness, whereas the patients with adjustment disorder reported more weight loss, reduced appetite, and insomnia. There was no significant difference between the groups in overall level of severity of depression or impaired functioning. The patients with depressive disorder NOS had a nonsignificantly elevated morbid risk of depression in their first-degree relatives.Clinically significant subthreshold depression was common in psychiatric outpatients, and the present results support the validity of distinguishing between depressive disorder NOS and adjustment disorder with depressed mood. Future studies of the treatment of subthreshold depression should account for this diagnostic distinction.