We evaluated the accuracy of posttraumatic stress disorder (PTSD) and major depression (MD) diagnoses using brief assessment instruments conducted by phone. PTSD and MD were assessed by telephone interview in a randomly selected sample of Jewish and Palestinian residents of Jerusalem (N = 150) during a period of marked threat of terrorism and war. We utilized the PTSD Symptom Scale Interview Format (Foa, Riggs, Dancu, & Rothbaum, 1993) and the Patient Health Questionnaire-9 (PHQ-9; Kroenke, Spitzer, & Williams, 2001). We then conducted in-depth, in-person interviews within 2 weeks, assessing PTSD and MD using the Composite International Diagnostic Interview (CIDI; Kessler et al., 2004). The prevalence of PTSD and MD diagnosis ascertained by the 2 assessment modalities was similar. Indices of classification accuracy for the phone interview, using the in-person interview as the standard, ranged from modest to high. Brief phone and in-depth in-person measures of PTSD and MD also correlated similarly with other demographic, stress, and coping factors, suggesting convergent validity. Brief phone interviews appear useful for estimating the prevalence of psychological disorders in mass casualty contexts and may have a critical role in both epidemiologic work and guiding public health interventions.