The kinetics of oxidn. of 1-butene with O on three types of bismuth molybdate catalysts were investigated in pulse expts. For all the catalysts mentioned the kinetics can be expressed by a first-order dependency on the butene pressure and a zero-order dependency on the O pressure. A slight deviation in the kinetics was observed for the Bi-Mo 2:1 catalyst, attributed to diene inhibition but not important enough to affect the kinetics. Low activation energies in the order of 10-11 kcal. mole-1 were found for all the catalysts over a wide range of temp. A high activation energy of 33 kcal. mole-1 was found with the Bi-Mo 2:1 catalyst at low temps. when butadiene was admixed to the pulses of 1-butene and O. A confirmation of the redn.-reoxidn. mechanism, proposed earlier, was obtained with the pulse technique.