For the determination of antibodies based on an immunoassay technique by incubation with at least three receptors R.sub.1, R.sub.2 and R.sub.3 which are present dissolved in a liquid phase and of which R.sub.1 is an antigen which is capable of being specifically bound to the antibody to be determined, R.sub.2 mediates the binding to the solid phase and R.sub.3 carries a label, separation of the complex which forms from the solution by binding to a solid phase and measurement of the label in one of the phases, a conjugate is used as the receptor R.sub.2 composed of a receptor capable of specific binding to R.sub.1 and a substance S.sub.1, which can be specifically bound, and a conjugate of a receptor which can specifically bind to R.sub.1 and a label is used as R.sub.3, wherein the immobilization of the complex which forms is mediated by binding to a component of the solid phase which can specifically bind S.sub.1.