We describe a new multianalyte immunoassay principle and apply it to the simultaneous immunoassay of lutropin, follitropin, choriogonadotropin, and prolactin in serum. The method is based on the coating of distinct areas of polystyrene with analyte-specific antibodies. These antibodies react with the analyte and immobilize it in a specific area while another biotinylated antibody also reacts with the analyte to form a sandwich. After addition of streptavidin labeled with the fluorescent europium chelate of 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid, fluorescent areas are formed, the intensity of which is related to the amount of each analyte present in the sample. The fluorescent areas are quantified on the dry solid phase with laser-excited time-resolved fluorometric measurements. The assays developed are highly sensitive, precise, and accurate. We believe that this system shows potential for multianalyte immunoassay of diverse groups of compounds in disciplines such as endocrinology, infectious disease, hematology, and oncology.