Cytokines are small protein molecules that are secreted by different cell types. Over the last decades the analysis of cytokine concentrations in serum and plasma has become an important research issue in several disease conditions. However, cytokine concentrations are usually not considered to be very stable after blood collection, which might therefore alter test results. A known source of error is the time period between blood withdrawal, arrival in the laboratory and processing of the sample. This study was intended to evaluate the influence of handling and storage conditions on detectable cytokines in human serum and plasma tubes. Furthermore, triggers for cytokine release from peripheral blood mononuclear cells (PBMC) were analyzed.