The electron donor–acceptor (EDA) interaction between methyl viologen (MV2+) and 1-naphthylamine (1NA), 2-naphthylamine (2NA), and N,N-dimethyl-1-naphthylamine (DMA) was studied in water and in aqueous sodium dodecyl sulphate (SDS). The experimental values of the association constants in water were 8.9, 9.8, and 2.8 M−1 for 1NA, 2NA, and DMA, respectively. In the presence of SDS the observed values were very much higher and strongly dependent upon the detergent concentration. The enhancement in the interaction is due to an increase in the local concentration of the partners in the micellar pseudophase. MV2+ itself was shown to strongly interact with the micelles. A new absorption is present at the red tail of the spectrum of MV2+ in the presence of SDS micelles. An association constant of 1700 M−1 was obtained from this absorption.