Cracking of neopentane was catalyzed by a sulfated oxide of zirconium promoted with iron and manganese. Reaction at 300-450 degrees C, atmospheric pressure, and neopentane partial pressures of 0.00025-0.005 bar gave methane as the principal product, along with C-2 and C-3 hydrocarbons, butenes, and coke. The order of reaction in neopentane was determined to be 1, consistent with a monomolecular reaction mechanism and with the formation of methane and t-butyl cations; the latter was presumably converted into several products, including only little isobutylene. At 450 degrees C and a neopentane partial pressure of 0.005 bar, the rate of cracking at 5 min onstream was 5 x 10(-8) mol/(g of catalyst s). Under the same conditions, the rates observed for unpromoted sulfated zirconia and USY zeolite were 3 x 10(-8) and 6 x 10(-9) mol/(g of catalyst s), respectively. The observation that the promoted sulfated zirconia is not much more active than the other catalysts is contrasted to published results showing that the former catalyst is more than two orders of magnitude more active than the others for n-butane isomerization at temperatures<100 degrees C. The results raise a question about whether the superacidity attributed to sulfated zirconia as a low-temperature butane isomerization catalyst pertains at the high temperatures of cracking.