The laser photolysis/chemiluminescence detection technique was employed to study the recombination reactions of the chlorine atoms generated by photolysis of chlorine molecules with 355 nm laser radiation in compressed Ar gas, The recombination rate constants, the quenching rate constants of the B (3) Pi(0(u)(+)) and A (3) Pi(1(u)(+)) states of the chlorine molecules by argon atoms, and the geminate recombination quantum yields were measured over 10-180 bar argon pressure. The recombination quantum yields were found to vary approximately as the third power of the argon density. For the present weak van der Waals system, the low-pressure asymptotic form of the energy relaxation/diffusion model and a simple molecular collision model were employed to account for the density-dependent behavior over the low-to-medium pressure range. The cage effect in the low-pressure regime and its related theoretical models were discussed.