BACKGROUND: Research on insight in patients with mood disorders has grown in recent years. Several instruments to assess insight have been used, but most of them have been specifically designed for psychosis and may not appear relevant to mood disorders. The aim of the present study is to develop a short, multidimensional, reliable and valid scale to measure insight in patients with mood disorders, based on the Amador's Scale to Assess Unawareness of Mental Disorders (SUMD). METHOD: A Delphi method was used to facilitate expert participation and ensure face and content validity. The SUMD structure and items were used as a reference in the scale development. A new scale with 17 items was obtained. Internal consistency, test-retest and inter-rater reliability and validity were studied in a sample of 76 outpatients with a DSM-IV diagnosis of major depression or bipolar disorder (type I or II). RESULTS: Internal consistency of the general items was moderate, and high for the symptoms awareness subscale. Scores on ISAD correlated with other measures of insight and with some clinical measures, thus supporting its validity. LIMITATIONS: The majority of the sample came from community services. Future studies should use inpatients or patients with severe symptoms to broaden the range of responses. Moreover, the rating of insight and other measures by the same clinician might introduce a methodological bias. CONCLUSION: The ISAD, with a multidimensional approach, appears as a short, reliable and valid measure of insight in mood disorders. Expert consensus ensures its face and content validity.