To evaluate the role of depression and mania in Tourette syndrome (TS), we have examined 246 TS patients, 17 attention-deficit disorder (ADD) patients, 15 patients with ADD associated with TS, and 47 controls, using (1) the standardized National Institutes of Mental Health Diagnostic Interview Schedule questions for a life history of major depression and/or mania and (2) a modified Beck depression score for evaluation of depression at the time of the examination. The results were combined into depression, Beck, and mania scores. Among the controls, 2.1% had a depression score greater than 9, and none had a score greater than 10. Among the TS patients, 22.9% had a score greater than 9 and the scores ranged up to the maximum of 18 (P less than .0005). None of the pure ADD patients had a score greater than 6, whereas 20% of the ADD-secondary-to-TS (ADD 2(0) TS) patients had scores greater than or equal to 9. Among grade 3 TS patients, 46.6% had scores greater than or equal to 9. There were no differences in the frequency of depression in the TS patients with or without ADD. Comparable results were obtained for the Beck depression score, except that the percent with a score greater than or equal to 8 was higher for the TS patients with ADD (23.7%) than for those without ADD (9.3%). There was a good correlation between the depression score and the Beck score (r = .63), but no correlation between the ADD-with-hyperactivity (ADDH) score and either the depression score (r = .086) or the Beck score (r = .077). Among the controls, none had a mania score greater than or equal to 4, compared with 19.1% of the total TS patients (P = less than .0005), 11.8% of the ADD patients (P = .002), and 26.6% of the ADD 2(0) TS patients (P = .0005). Although some of the mania questions would be expected to be answered positively by ADDH patients, the correlation coefficient between the ADDH scores and the mania scores was only moderate (r = .29), whereas the correlation with the depression score was much higher (r = .63). There was minimal correlation between the number of tics and either the depression score (r = .267) or the Beck score (r = .193). We conclude that depression and manic-depressive symptoms are common in TS patients and are an integral part of the disorder rather than being secondary to motor or vocal tics.