Triruthenium dodecacarbonyl (Ru-3(CO)(12)) adsorption and decomposition on titania (TiO2) were studied using infrared reflection absorption spectroscopy, temperature-programmed desorption, Auger electron spectroscopy, and scanning tunneling microscopy. It was found that the vapor-deposited cluster adsorbs with the R-U3 plane oriented normal to the surface. The clusters form an amorphous layer at 90 K, order at 195 K, and begin to decompose in a vacuum at ca. 250 K. The clusters decompose in two stages, with complete decomposition occurring above 600 K. The clusters are highly dispersed on the surface and decompose cleanly to form small ruthenium clusters up to 3 nm across and single atom rows up to 20 nm long.