Between 1969 and 1990 six patients (aged 14 to 64 years, mean 43 years) underwent in situ reconstruction for mycotic aneurysm of the ascending aorta. The primary source of infection was endocarditis in three patients (subacute bacterial endocarditis [n = one patient], sepsis with acute endocarditis [n = one patient]), sepsis with sternal osteomyelitis in one, sepsis with purulent pericarditis in one, and generalized febrile illness in one. In five of six patients the treatment consisted of the excision of changed tissue combined with a composite graft (n = one patient), a xenopericardial patch repair (n = one patient), a Dacron graft repair and aortic valve replacement (n = one patient), a Dacron graft repair alone (n = one patient), and a lateral suture combined with double valve replacement (n = one patient). In one patient with perforation of the mycotic aneurysm into the pulmonary artery, the place of rupture was oversewn without excision of the aortic or pulmonary artery tissue. Two patients with local pericardial inflammation were reoperated on during the hospital stay; one of them because of recurrent mycotic aneurysm of the ascending aorta at the other location and the other because of infection of the suture line after the Dacron patch repair. Antibiotic therapy was intravenously administered for 2 to 12 weeks postoperatively and continued orally for 4 to 8 weeks. The mean observation time was 6 years (range 4 months to 16 years). There was no late graft infection, except the chronic infection of the suture line in one patient who died suddenly 4 months after the operation. There was no early death, and there were three late deaths (chronic myocardial failure, one patient, chronic renal failure, one patient, sudden death, one patient). We concluded that in situ reconstruction for mycotic aneurysm of the ascending aorta combined with prolonged antibiotic therapy is an appropriate procedure with satisfactory early and good long-term results.