Abstract Background: Insight has been defined as: (1) recognition of symptomatology, (2) the ability to attribute symptoms to a mental health disorder, and (3) complying with treatment. Insight is related to medication compliance, course of illness and outcome. Current instruments for measuring insight are limited to those that have been validated primarily in hospitalized patients with psychosis. Our objectives were to develop a reliable and valid self-report scale for use in outpatients or inpatients with mood disorders. Toward this end we made extensive revisions of the Birchwood et al. [1994, Acta Psychiatr. Scand. 89, 62] Insight Scale for Psychosis. Methods: The scale was developed by modifying items from a previous self-report scale. Specifically, assumptions of hospitalizations, psychosis, and current symptomatology were removed and items related to mood state were added. The scale was included in a battery of measures completed by outpatients and inpatients participating in a study of mood stabilizer medications. Results: Subjects ( n=101, 66.3% female, median age 44 years) took approximately 2–3 min each to complete the scale. Overall scores were high (Mean=10.3 out of 12). Reliability was determined using test–retests ( r=0.75, n=45). Validity testing was based mainly on clinician ratings ( r=0.49, n=69). Conclusion: The new scale shows promise as a quick method for assessing insight in patients with mood disorders.