Patients with Parkinson's disease (PD) are known to experience autonomic nervous system dysfunction; this disruptive symptomatology includes urinary urgency, frequency, and nocturnal polyuria. Anticholinergic and tricyclic medications can be beneficial in controlling these urinary symptoms, but have unpleasant side effects in some patients. Desmopressin has been used to treat nocturnal polyuria successfully in a number of conditions, such as central diabetes insipidus, enuresis, and autonomic failure. The purpose of the present study was to assess the efficacy of desmopressin in patients with PD with significant nocturia. Eight patients were recruited into the study. They were first asked to establish a baseline of number of nocturnal voids; the patients were then prescribed the intranasal form of desmopressin and asked to continue to record the number of nocturnal voids. The five patients who completed the trial demonstrated clinically and statistically significant reductions in the frequency of nocturnal voids. One patient became hyponatremic and confused during desmopressin administration; his symptoms resolved soon after the desmopressin was discontinued. Two patients failed to complete the trial due to compliance problems. Thus, desmopressin appears to be a safe and effective medication for nocturnal polyuria in PD.