The photolysis of ketene in the presence of hydrogen has been investigated in the temperature range −40° to 207 °C. The main products are CO, C2H4, C2H6, and CH4, with some methyl ethyl ketone at the higher temperatures. Hydrogen and ketene compete for CH2radicals by the reactionswithE3 − E2 = 0.8 kcal. At the higher temperatures the reactionleads to a chain reaction viaThe value ofE6is found to be 10.2 ± 0.5 kcal. in good agreement with previous work.