Langmuir-Blodgett (LB) layers of 16-(9-anthroyloxy)palmitic acid (Atl) and C-60 mixed with tricosanoic acid have been studied as a model system for photoinduced electron transfer (PET). The PET has been investigated by monitoring the quenching of AA fluorescence in mixed LB films containing different concentrations of C-60. Perrin＇s hard-sphere model adapted for the two-dimensional case provides a good fit to the experimental results, confirming the two-dimensional nature of the system. The critical radius is found to be 11 Angstrom.