Objectives: to evaluate the plasma IL-10 levels during elective operative repair of thoraco-abdominal and abdominal aortic aneurysm repair. To study whether IL-10 plasma levels ae associated wit the duration of cross-clamping (ischaemia) and clinical outcome. Materials: fifteen consecutive patients undergoing surgery for TAAA and 10 consecutive patients undergoing surgical repair of AAA were included. Methods: plasma concentrations of IL-10 were measured by ELISA technique. Clinical outcome of the TAAA patients was prospectively analysed. Results: during aortic clamping IL-10 was produced in both populations. The plasm IL-10 peak (934 +/- 172 pg/ml) of the TAAA group was seen at 4 h after declamping and remained detectable after 48 h. The plasma IL-10 peak (212 +/- 32 pg/ml) of the AAA group was seen 30 min after declamping and fell to undetectable levels by 24 h. These data show that the peak IL-10 plasma levels in TAAA repair are significantly (p < 0.05) higher compared to the peak IL-10 plasma levels as seen during AAA repair. A positive correlation was seen between cross-clamping and peak plasma IL-10 and organ dysfunction. Conclusions: IL-10 plasma concentrations appear higher, later and are longer detectable in patients undergoing TAAA. Correlations were seen with duration of cross-clamping and MSOD.