To investigate the clinical significance of intraoperative cultures, aneurysmal thrombus was cultured in 176 patients with clinically non suspected infected abdominal aortic aneurysm. The incidence of positive cultures was 14.2% and 88% of the microorganisms were Gram-positive. Differences between elective and urgent reconstruction were not significant. During follow-up, there were no cases of graft infection in either group. Review of the literature shows a positive culture rate of 19% in a series of 1867 patients. 93% Of the microorganisms are Gram-positive and 78% are considered as contaminants. The incidence of graft infection is 1.99% in the group with positive culture and 0.7% in the series with negative culture (P = 0.06). It is concluded that the clinical significance of routine cultures in clinically non suspected infected aortic aneurysms is negligible.