The purpose of the present study was to document the increased leukocyte adhesiveness/aggregation (LAA) and tissue leukostasis that follow surgical trauma. We found that following major abdominal surgery, the percentage of aggregated leukocytes in the peripheral blood increased from 8.6 +/- 7 to 21.7 +/- 11.5 (p < 0.001), while the respective values for patients undergoing minor surgery were 3.7 +/- 2.4 and 19.7 +/- 7.6% (p < 0.001). The state of LAA was also determined in eight dogs after partial collectomy and four controls. A clear increment in the degree of tissue leukostasis (especially in the spleen, liver and lungs) was noted in the operated as compared to the control animals. In addition, a significant correlation was found between the state of LAA, determined in the venous (p = 0.0004) and arterial (p = 0.002) blood of these animals and the degree of tissue leukostasis. We conclude that a state of increased LAA in the peripheral blood is induced by surgical trauma and that this increased LAA correlates with tissue leukostasis.