The hemodynamic effects of triglycyl-lysine-vasopressin (TGLVP) were investigated in a single-blind study in seven patients with chronic orthostatic hypotension and parkinsonism. Blood pressure, heart rate, and stroke volume were measured in the supine position before and after bolus injection of either placebo or TGLVP (5.0, 7.5, or 10.0 micrograms/kg of body weight). After 40 min in the supine position, the patients were head-up tilted to 45 degrees for 20 min. All patients underwent four tilt studies with different medication. The TGLVP increased supine blood pressure by approximately 25% and total peripheral resistance by approximately 46%, and reduced heart rate by approximately 13%. No changes in supine stroke volume or cardiac output were seen. The TGLVP slightly reduced the relative fall in blood pressure and increased heart rate during the tilt. After TGLVP, blood pressure levels during tilt were similar to supine levels prior to medication. The TGLVP did not change the effects of tilt on stroke volume or cardiac output. Only few and mild side effects were experienced and no cardiotoxic effects were observed. In conclusion, TGLVP showed marked blood pressure effects of very small doses in this category of patients. The clinical effects of TGLVP and other vasopressor-specific analogs of vasopressin should be tested in these patients.