The binding of two model photodynamic therapy drugs, chlorin p6 and purpurin 18, with surfactants has been studied using steady-state and time-resolved fluorescence techniques. The surfactants used are amphiphilic nonionic surfactant (Tween 80 and Tween 40) and zwitterionic surfactant (HAPS). These have applications in drug delivery. The studies have been performed at pH 7 and 5 for chlorin p6 and at pH 7 for purpurin 18. The binding constants have been estimated from the change in fluorescence parameters and have been compared with those for Cremophor EL and human serum albumin. Chlorin p6 is found to bind to the surfactants to a greater extent at pH 5 than at pH 7. The same ionic species of chlorin p6 is found to exist at the maximum concentrations of the surfactants.