The Clinical Interview Schedule Revised (CIS-R) was validated in a clinic setting for adolescents 15-19 years of age in Sri Lanka. The interview schedule was translated into Sinhala and modified to include sections introducing each symptom group. One-hundred-and-thirty-one adolescents attending a psychiatric clinic for the first time were interviewed by a lay interviewer using CIS-R (Translated). They had previously been examined and rated by a psychiatrist using local (emic) diagnostic procedures. All the filtering questions showed a high level of sensitivity (80%-96%). None of the questions in the sleep problems and phobias sections were effective at discriminating between those who did and did not show significant symptoms in these areas according to the psychiatrist. The internal consistency of the sections of the interview schedule (when these two sections were excluded) varied between 0.60 and 0.82. Linear regression showed that, when both sections were excluded, 97% of the variation of total score could be explained. Therefore, it was decided to exclude the sleep problems and phobias sections from the modified interview schedule. As the population samples are likely to be different from clinic samples it is necessary to test the validity again in a community sample before confirming the validity of the modified interview schedule.