AbstractSerum gastrin levels did not change during topical corticosteroid therapy with an experimental dose of 20 to 60 g/day for seven consecutive days, and serum 11‐hydroxycorticosteroid levels were significantly suppressed during the treatment. On the other hand, after daily oral administration of 1.5 mg/day betamethasone for seven consecutive days in volunteers who had fasted overnight, serum gastrin levels were higher and 11‐hydroxycorticosteroid levels were significantly lower.Fasting serum gastrin levels were significantly increased in rats after intraperitoneal administration of prednisolone at dosages of 2, 10, 20, or 50 mg/kg/day, but they were not significantly altered after the administration of prednisolone at 0.5 mg/kg/day. Serum gastrin levels were not significantly altered in man or rats after the administration of a histamine H1receptor antagonist. Therefore, serum gastrin levels are apparently not influenced by topical corticosteroid treatment although they are altered after systemic corticosteroid administrat