1. With the aid of butane labeled with radiocarbon, the dehydrogenation of butane-butene mixtures was investigated over an alumina-chromia catalyst. The relative rates of the dehydrogenation of butane and butene to butadiene in presence of a chromium oxide catalyst were calculated from experimental data obtained previously. 2. It was shown that the ratio of the rates of dehydrogenation of butane to butene and of butane to butadiene is of the same order for the two catalysts and has a value of about 20 : 1. In experiments with the chromium oxide catalyst the ratio of the rates of formation of butadiene from butane and from butene is 1 : 1000, whereas in experiments with the alumina-chromia catalyst this ratio is 1 : 25. 3. It was confirmed that the formation of butadiene from butane proceeds through the stage of butene, which, before being converted further into butadiene, is desorbed from the surface into the bulk phase to an extent of not less than 95 %. 4. It was shown that the constants in the denominator of the kinetic equation for dehydrogenation are adsorption coefficients.