Plasma concentrations of the major dopamine (DA) metabolite homovanillic acid (HVA) are useful indicators of brain DA activity1 in clinical research2, 3. It is the potential index of central dopamine turnover4 and is the most suitable instrument currently available to assess DA activity under relatively natural behavioral conditions i. e., without any pharmacological manipulation or inducing stress from study conditions5. In this study, We compared the plasma homovanillic acid (pHVA) concentration in the delusional disorder patients as well as in the healthy controls to investigate if the abnormalities of the central dopaminergic transmission may involve in the expression of the delusional symptoms in the patients. 30 Delusional disordered patients have been considered for this study. 30 age and sex matched healthy individuals were considered as the control. A significant increase has been found in pHVA concentration of delusion disorder patient than the healthy controls. The finding suggests that there is a positive correlation between pHVA concentration and delusional disorder, which further provides the evidence for hyperdopaminergic activity in the brain of delusional disorder patients.