Abstract: A biologically recognizing layer on a solid phase consisting of biologically recognizing molecules comprising regions which recognize a substance to be analyzed and regions which do not recognize a substance to be analyzed.The biologically recognizing molecules are aligned on a suitably modified surface by means of molecular regions which do not recognize the substance to be analyzed. The biologically recognizing molecules are cross-linked with the aligning surface and are consequently covalently altered. The molecular regions recognizing the substance to be analyzed are not altered by the covalent bonding and retain their bonding activity.The layer is produced in a novel two-stage method. In the first step, the biologically recognizing molecules, the aligning molecules and carrier molecules are adsorbed. In the second step, the molecules are covalently anchored by cross-linking. Cross-linking is brought about by photolytic activation of a water soluble reagent bonded to the carrier molecules.