The excited-state proton transfer from 4-hydroxy-1-naphthalenesulfonate to urea has been studied in methanol at 25 degrees C. The decay of the acidic form is single-exponential for ail urea concentrations. The proton acceptor concentration has been found to increase nonlinearly with the concentration of urea. The nonlinear behavior is explained by a model proposing urea monomers and, in particular, urea dimers to be the proton accepters in methanol.