Abstract: A receptor preparation of biologically active receptor material is produced in which a cell membrane preparation is lyophilized accompanied by the addition of sugars and/or amino acids and/or proteins. A radioreceptor assay can be produced therefrom, which contains the colyophilizate of cell membrane together with sugar compounds and/or amino acids and/or proteins, as well as a tracer substance and a comparison standard substance. A radioreceptor assay kit uses the radioreceptor assay by making available the substances in a plurality of test containers containing a colyophilizate suitable for the assay.