Oxidative dehydrogenation of adamantane and 1,3-dimethyladamantane (1,3-DMA) to dehydroadamantanes was studied in the pulse mode at 150-250degreesC in a flow of helium or air (with air oxygen or H2O2 as an oxidant) in the presence of the polyoxometalates K5FeSi(OH2)W11O39 (.) 3H(2)O and Na6MnSi(OH2)W11O39 supported on Al2O3.. Dehydrogenation was shown to proceed only on the iron-containing polyoxometalate (POM). In an air stream, adamantane forms 2,4- and 1,3-dehydroadamantanes, whereas 1,3-DMA gives 4,6 and 4,8-dehydro-1,3-dimethyladamantanes in a ratio of 3 : I and 2.3 : 1, respectively. The maximum yield of dehydroadamantanes at 250degreesC in an air flow was 0.8 wt %, and that of dehydro-1,3-dimethyladamantanes was 3.0 wt %. In a helium flow, the dehydrogenation of 1,3- DMA occurs at 250degreesC with a 0.2% yield of dehydrogenation product. With H2O2 used as an oxidant in a helium stream, the dehydrogenation of 1,3-DMA yields 4,6-, 4,8-, and 4,9-dehydro- 1,3-DMA (1 : 1.6: 1.6). The electron ionization mass spectra are given, and the fragmentation of dehydro-1,3-DMA is discussed.