The development and psychometric properties of the Stressful Life Events Schedule (SLES), an interview instrument to assess stressors in children and adolescents, are described. Children (< or =12 years) and adolescents (>12 years) with psychopathology (n=30) and non-psychiatric controls (n=30) were interviewed with the SLES about the occurrence of stressful life events during the prior year. To examine concurrent validity of the SLES, all subjects also completed the self-report Life Events Checklist (LEC) and half the sample completed the Life Events and Difficulties Schedule (LEDS). To examine informant validity, the parent/guardian also reported on stressful life events occurring to their child during the year prior to interview. Test-retest reliability of the SLES was examined by re-assessing all children approximately one week after the initial interview. Subjects rated subjectively how stressful an event was on a 4-point scale. Additionally, panel ratings of objective stress and behavior-dependence/independence were made on 4-point scales. The SLES was found to have substantial inter-rater consensus reliability for objective threat (kappa=0.67) and almost perfect reliability for event behavior-dependence/independence (kappa=0.84). Similarly, the test-retest reliability of the SLES was also found to be substantial at the level of specific event comparisons (kappa=0.68). The SLES discriminated between children with and without psychopathology on all measures of stressful life events. Total stressful life events assessed with the SLES concurred well with those assessed by the LEC (ICC=0.83) and the LEDS (kappa=0.77) although, as expected, examination of specific events showed much smaller overlap between the SLES and the LEC (kappa=0.26). Child-parent agreement for the occurrence of severe events was substantial (kappa=0.73) but tended to be only moderate when all events were examined (kappa=0.48). The results of this study indicate that the SLES has good psychometric properties. The SLES is a useful, cost-effective tool for assessing stressful life events in children and adolescents.