The photochemistry of Fe(CO)(5) adsorbed on silver at 89 K has been investigated by time-of-flight mass spectrometry, thermal desorption spectroscopy, and photon-induced desorption. These measurements were made as a function of coverage, decane spacer layer thickness, and surface roughness. Photodissociation yields CO in the gas phase. Wavelength dependent studies of the cross-section suggest an adsorbate-mediated mechanism. Time-of-flight data reveal both translationally hot and thermalized CO products, the latter being more prominent when the adsorbate is not directly adsorbed onto the silver surface. The photochemical cross-section is found to be larger for Fe(CO)(5) adsorbed directly onto silver than for adsorption onto decane or for multilayers. In contrast the photochemical yield is larger for multilayer coverage. It is proposed that this is in part due to the existence of dark reactions between the photoproduct and the reactant, which occur more readily in multilayers. The effect of extensive roughening of the surface is to enhance the photochemical cross-section by at most a factor of 2. This suggests that surface-plasmon-enhanced photochemistry is of only minor importance in this case.