Elevations of serum immunoreactive interleukin 6 (IL-6) and Group II phospholipase A2 (M-PLA2) were observed without exception after elective surgeries for various sites. Serum IL-6 rose steeply after surgery, and reached the maximum level on the 1st postoperative day. Serum M-PLA2 increased from the 1st postoperative day and reached the maximum level on the 2nd postoperative day in 10 patients (76.9%), on the first day after surgery in 2 patients and on the 3rd day in one patient. The peak serum M-PLA2 after surgery was significantly correlated with the peak IL-6 and blood loss volume during surgery. These results suggested that serum M-PLA2 is an acute phase reactant.