The authors examined dose-response relationships in 62 agoraphobic patients receiving either imipramine or placebo under double-blind conditions in conjunction with behavioral interventions. At the end of 12 weeks, patients treated with imipramine had improved significantly more than placebo patients. Results revealed that the beneficial therapeutic effect of imipramine was dose dependent and suggested that optimal response in agoraphobia may require doses of 150 mg/day or more. The results also indicated that side effects can significantly interfere with the buildup of optimal dose in agoraphobic patients treated with imipramine. The authors briefly discuss the implications of these findings for clinical practice and future research.