OBJECTIVE To study the clinical effectiveness of biofeedback treatment in reducing tics in patients with Tourette syndrome. BACKGROUND Despite advances in the pharmacologic treatment of patients with Tourette syndrome, many remain troubled by their tics, which may be resistant to multiple medications at tolerable doses. Electrodermal biofeedback is a noninvasive biobehavioral intervention that can be useful in managing neuropsychiatric and neurologic conditions. METHODS We conducted a randomized controlled trial of electrodermal biofeedback training in 21 patients with Tourette syndrome. RESULTS After training the patients for 3 sessions a week over 4 weeks, we observed a significant reduction in tic frequency and improved indices of subjective well-being in both the active-biofeedback and sham-feedback (control) groups, but there was no difference between the groups in these measurements. Furthermore, the active-treatment group did not demonstrably learn to reduce their sympathetic electrodermal tone using biofeedback. CONCLUSIONS Our findings indicate that this form of biofeedback training was unable to produce a clinical effect greater than placebo. The main confounding factor appeared to be the 30-minute duration of the training sessions, which made it difficult for patients to sustain a reduction in sympathetic tone when their tics themselves were generating competing phasic electrodermal arousal responses. Despite a negative finding in this study, electrodermal biofeedback training may have a role in managing tics if optimal training schedules can be identified.