Adsorption of C-60 molecules on Si(lll)-(7x7) has been studied using scanning tunneling microscopy under ultrahigh vacuum conditions at a variety of temperatures and coverages. At submonolayer coverages, isolated C-60 molecules were found to adsorb preferentially in the areas near the three midadatoms within a half unit cell of (7x7) symmetry. At monolayer coverage, the adsorbate-adsorbate interaction changes the molecular bonding sites and causes the local ordering of the C-60 adlayer. Thermal annealing to temperatures above 800 degrees C causes the decomposition of C-60 molecules on the Si surface and the formation of SIC clusters.