Eighty cocaine-dependent individuals enrolled in outpatient treatment took part in a randomized, double-blind, placebo-controlled trial of ritanserin, a 5-HT(2) antagonist, as an adjunct therapy. Participants attended an outpatient day hospital therapy program each day and received tablets containing placebo or 10 mg ritanserin for a 4-week period. Primary outcome measures included retention in treatment, urine drug tests, and self-reports of craving. Secondary outcome measures were depression scores on the Beck and Hamilton inventories, negative mood as measured by the Profile of Mood States, and life functioning as measured by the Addiction Severity Index. Although participants showed improvement over the 4 weeks, there were no group differences on any of the measures. These results fail to support the use of ritanserin as a complement to outpatient psychosocial therapy for cocaine dependence.