Human capillary blood was placed in drops on hydrophilic or hydrophobic glass surfaces and incubated in a humid chamber at 37 o C for time periods of 5 s through 48 h. The blood was rinsed off, and the adhering cells were typed with antibodies directed against cell differentiation antigens (International Cluster Determinant, CD 14, CD66b and CD99R) or pan-platelet antigen, detected by immunofluorescence. The number of adhering cells was quantitated with computer-aided image analysis. Blood cells appeared on the surfaces in sequential order, partly correlated with the number and size of the cells in peripheral blood. Platelets were seen at both surfaces after 5-30 s of blood exposure and were present at both surfaces after 24 h exposure time, in higher numbers at the hydrophobic surface. Neutrophils where found after 8 min of blood exposure, with a defined peak at 32 min, and only a few cells after 24 h exposure time. Monocytes were seen after 2 h of exposure at both surfaces, the number of adhering cells increased with time for up to 48 h exposure time. Lymphocytes adhering to the surfaces were found after 32 min of blood exposure and where still present at the surfaces after 48 h exposure time. The numbers of lymphocytes were higher at the hydrophilic surfaces after exposure for 8 h or longer. Adhering cells showed intact esterase pool and were impermeable to propidium iodide. The data thus show differences in the kinetics of cell adhesion from whole blood onto hydrophilic and hydrophobic glass surfaces.