To determine what effect Methergine has on the blood pressure of the immediately postpartum patient, a series of 200 consecutive patients was studied. A group of 200 patients who received the usual ergonovine was used as controls. All patients were delivered vaginally and all received the drug intravenously. A striking similarity between the two groups is shown by a comparison of age distribution, parity, method of delivery, and anesthetic used. The average age of the Methergine patients was 28.5 years and that of the ergonovine patients was 29 years. In the Methergine group, 41.5 per cent were gravide i and 34.5 per cent were gravida ii; in the ergonovine series, the figures were 43.5 per cent and 31.5 per cent, respectively. Delivery was spontaneous in 30.5 per cent of the Methergine patients and 29.5 per cent of the ergonovine patients; by forceps for 62 per cent of the Methergine group and 64 per cent of the ergonovine group.A history of hypertension during the pregnancy was found in 4.5 per cent of the Methergine patients and in 5.0 per cent of the ergonovine patients. In the Methergine group, 22.2 per cent had significant rise in blood pressure after the drug was given and in the ergonovine group 60 per cent had increases. Methergine apparently is more likely to cause the diastolic pressure to rise, while ergonovine seems to affect the systolic pressure more frequently. With both drugs, the blood pressure effect is very rapid, occurring within one minute of administration in most cases. Excluding those cases in which large amounts of blood were lost, in neither of the two groups did the drug cause a drop in blood pressure.In the Methergine group, of the patients without history of hypertension, 32 had abnormally high blood pressure on admission, and in the ergonovine group, 38 patients had elevated blood pressure on admission. After Methergine was given, 6.25 per cent had increased blood pressure and after ergonovine 13.1 per cent had elevated blood pressure.Of the patients with no history of hypertension and normal blood pressure on admission, the blood pressure was increased in 11.3 per cent of those who received Methergine and in 31.6 per cent of those who were given ergonovine. With both drugs, blood pressure elevations usually occurred within five minutes of the administration of the drug. The systolic pressure was increased much more frequently than the diastolic.For the entire group of patients who received Methergine, 11 per cent had significant blood pressure elevations following administration of the drug, whereas 29.5 per cent of those who received ergonovine had a significant rise.