We carried out a double-blind, randomized, parallel-groups clinical trial of fluoxetine (20-40 mg/day) and placebo in 11 children with Tourette's syndrome (TS) and associated obsessive-compulsive symptoms (OCS). The treatment period lasted 4 months. No significant differences between treatment groups were observed for measures of OCS. Fluoxetine therapy, however, was associated with a trend toward some improvement in tic severity, attentional abilities, and social functioning. Given these observations and the limitations of this pilot study, which include selection biases, small sample size, and significant placebo effects, the efficacy of fluoxetine in children with TS deserves further larger-scale investigation.