Polystyrene microtitre wells are commonly used as supports for the enzyme-linked immunosorbent assay (ELISA) method of biomolecular detection, which is employed in the routine diagnosis of a variety of medical conditions. We have used an atomic force microscope (AFM) to directly monitor specific molecular interactions between individual streptavidin and biotin molecules on such wells. This was achieved by functionalising an AFM probe with biotin and monitoring the adhesive forces between the probe and a streptavidin coated immunoassay well. The results demonstrate that the AFM may be employed as an analytical tool to study the interactions between biomolecules involved in immunoassay systems.