Mixed metal oxide nanocrystals of AP-Al2O3, AP-Al2O3-Fe2O3, AP-Al2O3-V2O5 and AP-Al2O3-CuO have been prepared by aerogel process. XRD data of prepared materials revealed the formation of nanocrystals with a size range of 3-15nm diameters. N2 BET investigations on these materials revealed larger values of surface area ranging from 350 to 540m2/g. Reactivity of these nanocrystalline materials against Yperite was examined by gas chromatography, gas chromatography-mass spectrometry and infrared spectroscopy techniques. AP-Al2O3-Fe2O3, AP-Al2O3-V2O5 and AP-Al2O3-CuO nanocrystals exhibited superior decontamination properties against Yperite than AP-Al2O3. The reactions exhibited pseudo first order behaviour. 100% of Yperite was found to be decontaminated on Al2O3-Fe2O3, Al2O3-V2O5 and Al2O3-CuO where only 75% of the same was found to be decontaminated on AP-Al2O3 within 40h. © 2010.