By making use of the 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) reducing ability of stimulated human neutrophils, we developed an alternative method to quantify the adherence of neutrophils in vitro. After discarding non-adherent neutrophils, the adherent cells were exposed to MTT solution containing 10 ng/ml phorbol 12-myristate 13-acetone (PMA). Subsequently, MTT reduced by this simultaneous stimulation was measured optically and used to calculate percent of adhesion. In these experiments, heat-inactivated autologous serum and tumor necrosis factor alpha (rhTNF-alpha) were observed to promote the adherence to polystyrene surfaces. In contrast, minimal or no effects on neutrophil adherence were achieved in case of treatment with native autologous serum, recombinant human granulocyte colony stimulating factor (rhG-CSF), recombinant human granulocyte-macrophage colony stimulating factor (rhGM-CSF), or recombinant human interferon gamma (rhIFN-gamma).