Abstract: A method for screening of modulators of calcineurin is provided, which uses the interaction between calcineurin and superoxide dismutase. Modulators of calcineurin are potential candidates for drugs, e.g. for immunosuppressive drugs. The forming of a complex comprising calcineurin and superoxide dismutase is monitorable in the presence of potential activators or inhibitors of calcineurin. Complex formation is performed within the cell by the use of appropriate expression vectors or in vitro using isolated proteins. Preferably, complex formation is monitored by fluorescence detection, especially by laser fluctuation correlation spectroscopy.