Carbon-13 and deuterium magnetic resonance data for propene adsorbed on high dispersion, alumina-supported platinum surfaces were obtained after adsorption at various temperatures and thermal treatments. Propene labeled with carbon-13 in the 1-position was found to scramble to the 3-position after exposure to 5% Pt/Al2O3, suggesting the formation of a short-lived propene allyl species. This species converts to a strongly adsorbed di-sigma-bonded configuration. Upon warming to 323 K, adsorbed propene is partially converted to propylidene. Our results indicate that propylidene decomposes to dehydrogenated surface carbon at elevated temperatures; neither ethylidene nor ethylidyne forms as a consequence of this decomposition.