A 53-year-old man was admitted with impairment of breathing following laryngeal edema. Serum levels of CH50 (22 U/ml), C4 (3 mg/dl), C1-INH protein (10.6 mg/dl) and C1-INH activity (LT 25%) were low. Complement study of the patient's family members revealed that he was one of 5 patients in 3 generations with hereditary angioneurotic edema (HANE). Administration of the androgen derivatives Danazol (600 mg/day) and Oxymetholone (30 mg/day) effectively increased serum levels of C1-INH activity and C4. Though eruption and hepatic dysfunction attributable to administration of the drugs appeared, these side effects improved after withdrawal of the drugs. Subsequently, the treatment with Danazol at a low dose (100 mg/day) was resumed, and the patient has had no episodes of edema for the past 3 years. Regarding the familial cases of HANE, fewer than 20 have been reported in Japan.