Stress has been linked to a broad range of psychopathology including alcohol and drug dependence. Recent advances in our understanding of how stress interacts with biological systems involved in addiction has generated even greater interest in stress assessment among addiction researchers. The Stressful Life Events Schedule (SLES) capitalizes on the strengths and avoids the pitfalls of self-report checklist and interview-based stress assessments. Because the SLES depends on consensus ratings of a research team, this study examined rater agreement of stressful event ratings across the first year using the SLES. Individual ratings of stressful events were compared between two experienced and three new raters. Ratings were analyzed for life events generated from interviews of 70 adolescent psychiatric inpatients and 62 healthy adolescents. Inexperienced raters, with backgrounds in addiction research, reliably rated stressful events and rater agreement improved over a year's time. Recommendations for successfully adopting the SLES for consensus rating are discussed.