There are various methods in measuring the ligand binding to receptors. A quantitative flow cytometric method of described for binding measurements of FITC labelled ligands to receptor coated micro beads. GpIIb/IIIa complex was purified from human platelets by affinity chromatography and coated to polystyrene micro beads. Fibrinogen (Fg) was labelled with FITC. Different concentrations of Fg-FITC with GpIIb/IIIa coated micro beads were incubated and analyzed by flow cytometry. BSA-FITC was used as a negative control. The Fg-FITC binding to isolated platelets was also studied under the same conditions. This method besides showing quantitative ligand binding to the receptor, it also reflects the in vivo binding conditions.