Eighty-five women at 28-36 weeks' gestation were studied prospectively in a clinical research center to assess a "roll over test" (RT) based on the original study by Gant et al. Patients were admitted to the hospital, placed on bed rest, and given a balanced diet. The test started 12 hours after admission. Blood pressure was measured every 10 minutes for an hour with the patient in the left lateral position, and then in the supine position for a second hour. The mean diastolic blood pressure was calculated in each position and the patients were sorted into 6 groups based on the magnitude of change in blood pressure. Seventeen patients developed gestational hypertension (GH). Only 3 of 20 (15%) patients with a positive RT developed GH, while 14 of 65 (22%) patients with a negative RT developed GH. Five of 12 patients who had an actual decrease in mean diastolic blood pressure also developed GH.