Modern development in physiopathology, diagnosis and medical treatment of haemocoagulative syndrome, allows to operate electively upon various organs and apparatus.3. 4. 8 Quite numerous appear in literature, particularly, the references regarding surgical operations,. performed in haemophilics. The availability of adequate preparations which replace the lacking factors of the coagulation, in fact, allows in such patient to arrive to a normal haemostasis as long as the length of the operation and during the post-operative period, with very low operative risk. In literature there is only one case2 regarding surgical intervention on haemophilics on cardiorespiratory apparatus. We think it worthwhile to report a case of voluminous abdominal aneurysm in an haemophilia B patient with good result. CASE REPORTThe patient was a 55-year-old male. Since childhood he noted the appearance of post-traumatic hematomas and haemorrhagic episodes of high intensity and duration during dental avulsions. In November 1970 he suffered of acute posteroinferior myocardial infarction. During 1971 the patient noted a pulsatile tumefaction in the mesogastric region. He was hospitalized in May 1971.On admission his general conditions were good. The blood pressure was 160/ 80 mmHg, the pulse 80, rhythmical, and the respirations were 16 for minute. The abdomen was irregularly globous due to the presence in the mesogastric region of a voluminous pulsatile tumefaction about 10 X 8 cm in diameter. The palpation confirmed the speculative character of the mass and, moreover, permitted to appreciate the smooth, regular surface of it, the elastic consistency and the reduced motion. The mass presented a typical expansive pulsation, with small retard on the peripheral pulses. A systolic murmur was heard on the tumefaction. The pheripheral pulses were slightly reduced bilaterally, especially on the left. The haemogenic tests revealed a haemocoagulative defect originated from lack of factor IX or haemophilia B. The abdominal roentgenogram showed an opacity of hemispheric form, on the right at the median line, immediately under the corresponding renal image, and extending from the II to V lumbar space, without calcifications, with pulsation synchronous with the arterial pulse. The electrocardiogram showed signs of old postero-inferior my-