Clinicians, provider organizations, and researchers need simple and valid measures to monitor mental health treatment outcomes. This article describes development of 6- and 10-item indexes of psychological distress based on the Symptom Checklist-90 (SCL-90). A review of eight factor-analytic studies identified SCL-90 items most indicative of overall distress. Convergent validity of two new indexes and the previously developed SCL-10 were compared in an archival sample of posttraumatic stress disorder patients (n = 323). One index, the SCL-6, was further validated with archival data on substance abuse patients (n = 3,014 and n = 316) and hospital staff (n = 542). The three brief indexes had similar convergent validity, correlating .87 to .97 with the SCL-90 and Brief Symptom Inventory, .49 to .76 with other symptom scales, and .46 to .73 with changes in other symptom measures over time. These results indicate the concise, easily administered indexes are valid indicators of psychological distress.