The photochemistry of CH3I adsorbed on Al2O3(0001) was studied using ultraviolet laser pulses at 266 nm. Desorbing photoproducts were detected using a mass spectrometer during photoexposure, and surface-adsorbed products were determined using thermal programmed desorption (TPD). The primary photoproducts were gas-phase iodomethane, gas-phase iodine, gas-phase methane, and gas-phase ethane. No other photoproducts were found in the gas phase or on the surface. The cross section for depletion of CH3I from the surface was 2.6 +/- 0.2 x 10(-19) cm(2). The total photochemical yield of gas-phase photoproducts increased with increasing coverage up to a total coverage of approximately 5 ML and then remained constant with further increases in coverage. A simple stochastic model with random adsorption was used to model these data and indicated a reaction depth of approximately 2 ML.