The leukocyte adhesiveness/aggregation test is a sensitive marker for the detection of inflammation and for the assessment of its intensity. This has been convincingly shown by several independent groups as well as in various models of infection/inflammation. However, it has not been settled whether the concomitant appearance of leukocytosis and aggregation is a result of chance collision or not. We recently examined a group of individuals with proven acute infection/inflammation who had absolutely the same number of white blood cells in the peripheral blood and found significantly enhanced leukocyte adhesiveness/aggregation in patients as opposed to control. These findings clearly demonstrate that the phenomenon of leukocyte adhesiveness/aggregation does not result from a simple chance collision. It probably conveys a message of biological relevance reflecting both the appearance of cell adhesive molecules during activation as well as the contribution of plasmatic sticky proteins.