Numerous studies have assessed the acute efficacy of antidepressants, including selective serotonin reuptake inhibitors, in treating dysthymic disorder; however, escitalopram, the S-enantiomer of citalopram, has not been studied. Thirty-six outpatients with Structured Clinical Interview for DSM-III-R-diagnosed dysthymic disorder, aged 23-65 years (mean±SD=44.7±11 years), were randomly assigned to double-blind escitalopram (maximum dose 20 mg/day) versus placebo for 12 weeks. Inclusion criteria included age 18-65 years and Hamilton Depression Rating Scale (HDRS) score≥12. We hypothesized that escitalopram would be superior to placebo in the HDRS-24 item total score at week 12. We also hypothesized the superiority of escitalopram over placebo for secondary measures, including the percentage of participants classified as responders and remitters, as well as social functioning (Social Adjustment Scale), clinical global impression-improvement, Global Assessment of Functioning Scale. Participants' baseline HDRS-24 averaged 23.4±5.9. Final HDRS-24 scores at last observation carried forward did not differ significantly between escitalopram-treated (mean±SD=10.88±5.83) and placebo-treated individuals (mean±SD=16.4±6.34) (F=2.82, degrees of freedom=1,32, P=0.10). Significant differences favoring active medication were found on the Social Adjustment Scale and the Clinical Global Impression Severity and Global Assessment of Functioning Scale, but not in the percentages of responders or remitters. A larger study sample or higher escitalopram dose may show more significant placebo-medication differences.