Hydrostatic (physical) pressure effects on the electrical resistivity of a bromido-bridged palladium compound, [Pd(en)(2)Br](Suc-C-5)(2)center dot H2O, were studied. The charge-density-wave to Mott-Hubbard phase transition temperature (T-pT) steadily increased with pressure. By a comparison of the effects of the chemical and physical pressures on T-PT, it was estimated that the chemical pressure by unit alkyl chain length, i.e., the number of carbon atoms in the alkyl chains within the counterion, corresponded to ca. 1.3 kbar of the physical pressure.