– BACKGROUND: Efforts to develop and validate fully-structured diagnostic interviews of mental disorders in non-Western countries have been largely unsuccessful. However, the principled methods of translation, harmonization, and calibration that have been developed by cross-national survey methodologists have never before been used to guide such development efforts. The current report presents the results of a rigorous program of research using these methods designed to modify and validate the Composite International Diagnostic Interview (CIDI) for an epidemiological survey in Nepal. METHODS: A five-step process of translation, harmonization, and calibration was used to modify the instrument. A blinded clinical reappraisal design was used to validate the instrument. RESULTS: Preliminary interviews with local mental health expert led to a focus on major depressive episode, mania/hypomania, panic disorder, post-traumatic stress disorder, generalized anxiety disorder, and intermittent explosive disorder. After an iterative process of multiple translations-revisions guided by the principles developed by cross-national survey methodologists, lifetime DSM-IV diagnoses based on the final Nepali CIDI had excellent concordance with diagnoses based on blinded Structured Clinical Interview for DSM-IV (SCID) clinical reappraisal interviews. CONCLUSIONS: Valid assessment of mental disorders can be achieved with fully-structured diagnostic interviews even in low-income non-Western settings with rigorous implementation of replicable developmental strategies.