The reaction of dimethylzinc on Si(100)‐2×1 was studied using temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). Dimethylzinc dissociated on this surface at temperatures less than 400 K producing zinc metal and surface methyl groups. During TPD experiments the zinc metal desorbed completely by 600 K, leaving only methyl groups on the surface at higher temperatures. The predominate decomposition pathway for the surface methyl species was complete dehydrogenation producing molecular hydrogen and depositing carbon on the surface. HREELS results indicated that methyl group dehydrogenation occurred at temperatures greater than 700 K. For high initial coverages of dimethylzinc, in addition to complete dehydrogenation products, methyl radicals and acetylene were also detected. The hydrogen desorption temperature was found to increase as a function of the amount of carbon deposited on the surface.