Abstract: The invention provides a method for detecting and determining one component of the reaction between a specific binding protein, e.g., an antibody, and the corresponding bindable substance, e.g., an antigen, by utilizing the affinity of these components for binding one another, in an automated system utilizing a continuously flowing stream of liquid. The method is carried out by introducing successive mixtures of the sample specimen with a set amount of one component of the reaction in tagged form and another, carrier-bound, component, into the liquid stream so that the individual mixtures remain separate, incubating the mixtures and continuously introducing same into a separating system in which at least a portion of the liquid phase is separated from the solid phase, and measuring the amount of the tagged component in one of the separated phases as a measure of the unknown component to be detected.