The response of endogenous norepinephrine levels (NE) to changes in body posture, lateral to supine, was investigated in a prospective study of 46 primigravid patients during the last half of pregnancy. Blood samples were obtained in the lateral and supine positions. The mean supine NE levels were not significantly higher in those patients destined to develop pregnancy-induced hypertension (PIH) than in those who remained normotensive. The mean percent relative change of NE in the patients destined to develop PIH and in those who remained normotensive was not significantly different.