Functional dyspepsia is a heterogeneous disorder that consists of a variety of upper gastrointestinal symptoms such as postprandial fullness, early satiety, pain, bloating, belching, or nausea. The pathophysiology of functional dyspepsia is not fully understood and the correlation of those proposed mechanisms with the clinical characteristics and treatment response is poor. Owing to the poor understanding on the mechanism, treatment of functional dyspepsia has been far from satisfactory. There are numerous modalities of medical treatment that has been reported to be effective but the results are conflicting. Large and well-controlled studies in functional dyspepsia have shown that proton pump inhibitor had a therapeutic gain of about 10%-15% better than placebo in patients with functional dyspepsia. However, this positive effect was restricted to patients with reflux-like dyspepsia, a subgroup that actually is no longer considered to belong to functional dyspepsia. Prokinetic agent is another class of drug that has been widely used in functional dyspepsia. Although recent reviews suggest that prokinetics are more effective than placebo, most trials were flawed with significant heterogeneity among studies. Tricyclic antidepressant (TCA) is another important class of drug that is commonly used in various functional gastrointestinal disorders (FGID) and chronic pain disorders. The effectiveness of TCA in FGID has been supported by a meta-analysis, which reported that improvement in global GI symptoms against placebo was highly significant. The mechanism of TCA in treatment of FGID is poorly understood but the therapeutic effect is evident even in low dose, suggesting that it is independent of its anti-depressive action. To date, clinical trial of TCA in treatment of FD with sufficient sample size and well-defined clinical endpoint is still lacking. So the objective of this study is to evaluate the efficacy of imipramine, a tricyclic antidepressant, in treatment of functional dyspepsia.