The CryIA(a), CryIA(b) and CryIA(c) Bacillus thuringiensis insecticidal crystal proteins (ICPs) were used in ligand-blot experiments to detect specific binding proteins in brush-border membrane vesicles (BBMV) of Manduca sexta. We identified a protein which binds these three CryIA-type ICPs. The apparent molecular mass of the protein, estimated on SDS-PAGE, was 210 kDa as was the CryIA(b) binding protein previously described by Vadlamudi and col. We have also demonstrated, in ligand blot experiments, that CryIA(a) and CryIA(c) compete with CryIA(b) for binding this 210 kDa protein. Properties of the binding molecule can be correlated with knowledge previously acquired through radiolabelled binding experiments.