The excimer formation and decay dynamics of pyrenesulfonate on a cationic micellar surface have been studied by measuring the decay of monomer fluorescence as well as the rise and decay of the excimer emission. The excimer formation rate constant, lifetime, and quenching rate constant by the monomer were found to be 2.1 x 10(7) s(-1), 46.2 ns, and 2.6 x 10(6) s(-1), respectively.