Micelle-like clusters of antibody molecules were prepared by covalent attachment of various hydrophobic groups to the protein molecules, These colloidal clusters were capable of solubilizing two hydrophobic probes, while the solubilizates:solubilizer molar ratio was dependent on the chain length of the hydrophobic groups, the degree of modification, and hence, on the size of the colloidal clusters, By using a fluorescent solubilizate, it was demonstrated that the immunoclusters may have a specific recognition ability.