The purpose of this study was to evaluate the therapeutic potential of the somatostatin analog octreotide in patients with orthostatic hypotension. Octreotide was administered sc, and its pressor effect was assessed while the patients were semirecumbent and on the tilt table. We also studied the effect of octreotide on blood pressure while patients walked. The efficacy of therapy was assessed by measuring the duration of walking (walking time) before the onset of hypotension. Low doses of octreotide (0.2-0.4 micrograms/kg) had a pressor effect in all patients with progressive autonomic failure (n = 7), multiple system atrophy (n = 7), and diabetic autonomic neuropathy (n = 8), but not in patients with sympathotonic orthostatic hypotension (n = 6). Larger doses (0.4-1.6 micrograms/kg) resulted in a sustained (greater than or equal to 50 min) increase in blood pressure during walking in four of six patients with progressive autonomic failure and in one of six patients with multiple system atrophy. Some patients in whom octreotide failed to stabilize upright blood pressure had a satisfactory response to the drug after pretreatment with dihydroergotamine (10 micrograms/kg, sc). Patients with diabetic autonomic neuropathy, although sensitive to the pressor effect of octreotide, often developed nausea or abdominal cramps after moderate doses (greater than 1.0 micrograms/kg). These results indicate that the pressor effect of octreotide is sufficiently potent to prevent orthostatic hypotension in some patients with autonomic neuropathy. Others require treatment with both dihydroergotamine and octreotide to achieve a stable upright blood pressure.