In autopsy specimens removed after gastrectomy from patients who had survived for 2.5 to 40 years after surgery, we found hyalinization of the islets of Langerhans in 9 of 15 cases (60%) with Billroth's I anastomosis (B-I) and in 8 of 16 cases (50%) with Billroth's II anastomosis (B-II). The hyalinization in the postgastrectomy patients was significantly increased compared with that in controls (p < 0.01). The percentage of hyalinized islets of Langerhans in the 17 cases showing hyalinization ranged from 0.2% to 14.3%. The percentage increased relative to the period after gastrectomy in the B-I patients but not in those with B-II. The blood glucose level was mildly elevated in three B-I patients, whereas it was increased in only one patient with B-II. Hyalinization of the islets of Langerhans may be due to vagotomy or to excessive stimulus and hyperactivation of the islets. In any event, the islets of Langerhans in patients after gastrectomy were frequently replaced by hyalinization, which might cause impaired glucose tolerance.