A method of detecting the binding of ligand molecules (mannosides) to a biological receptor (Con A) by Forster energy transfer from Langmuir-Blodgett (LB) films is presented. The LB films consist of pre-polymerized amphiphilic polymethacrylates containing a coumarin fluorophore (donor) and reactive groups to which biological receptors can be attached. Studies determining the stability of the system are described. The specific binding of rhodamine (acceptor)-labelled ligands and their competitive replacement by unlabelled analytes is demonstrated. A simple dual-channel fluorescence detector optimized for this purpose is described as well.