We report here, for the first time, magnetic-field-effect (MFE) quenching of pyrene-DMA exciplex luminescence in SDS micelles as a function of Gd3+ concentrations. The MFE quenching, in contrast to neat-solvents, varies non-linearly. We believe that NIFE reduction depends linearly on [Gd3+] at the micellar-interface, but the Gd3+ adsorption at the micellar-interface depends non-linearly on bulk [Gd3+], which accounts for the observed non-linearity. We propose that Temkin isotherm is applicable here. This is the first time, we believe, that it has been demonstrated that it is possible to probe the adsorption of trivalent lanthanides on the SDS micellar-interface through highly sensitive MFE studies. (C) 2004 Elsevier B.V. All rights reserved.