The oxidation of gaseous butane has been investigated in the range 260 °C. to 540 °C. with reaction vessels differing greatly in surface to volume ratio. Increased surface area retards the reaction. The rate–temperature relation shows a maximum and a minimum. At low temperatures the rate is very sensitive to temperature, the apparent activation energy being greater than 100 kcal. The abnormal temperature coefficients are shown to arise in part from the differing response to temperature of the branching reactions and the initiation reactions, and in part from the occurrence of competing reactions.