The aim of this work was to determine whether there is a pre-established basal condition of the endothelial cells isolated from aortic abdominal aneurysm that might augment immune effector mechanisms and thus provide us an insight into the possible causes of aneurysm rupture. Endothelial cells isolated from saccular aortic aneurysm fragments were analyzed by cytofluorometry for the expression of different immune response-related molecules. Our results showed that there is a subpopulation of granule-rich, CD105 positive and von Willebrand antigen negative endothelial cells that have an enhanced basal expression of ICAM-1, and Fas antigen, but, interestingly, no apoptotic bodies were detected. Control endothelial cells derived from healthy areas of the same abdominal aortas did not show such enhanced expression. We conclude that in the endothelium that lines abdominal aorta aneurysms there is, at least, one endothelial cell subpopulation with an apparent inhibition of programmed cell death and in a proinflammatory activation status.