Sixty-four patients with acromegaly were retrospectively analyzed to study the incidence and cause of hypertension in acromegaly. WHO criteria indicate that 37.5% patients with acromegaly have hypertension. The blood pressure was positively correlated with age, the insulin-like growth factor I (IGF-I) and serum sodium (Na) concentration. In addition, IGF-I and Na were significantly different in hypertensive and normotensive groups. Seventy-five percent of hypertensive patients had a family history of hypertension. IGF-I, Na and blood pressure were significantly higher in patients with a family history of hypertension than in those without it. In patients with a family history of hypertension, blood pressure was positively correlated with IGF-I and serum Na, but IGF-I was not correlated with serum Na. In patients without such a family history, blood pressure had a good correlation only with age, and IGF-I was not significantly correlated with blood pressure. In addition, the incidence of hypertension in this group was the same as or lower than that in the general population. The above results suggest that the genetic factor produces hypertension in acromegaly by two ways, by increasing Na and enhancing IGF-I production by GH.