We report a new partially automated method for the measurement of the adherence of PMN in vitro. Adherence to a plastic surface was detected by measuring leukocyte alkaline phosphatase activity of the adherent cells, with a Titertek Multiscan system. Using three different cellular concentrations (1 X 10(6), 5 X 10(5), 2.5 X 10(5) PMN/ml) the response curve was linear to 45 min and adhesion was maximal by 30 min. The specificity of the reaction was acceptable as was the assay reproducibility (intra-assay coefficient of variation less than 8%; inter-assay coefficient of variation less than 11%).