The millisecond autothermal reforming of benzene, toluene, ethylbenzene, cumene, and styrene were independently studied over,five noble metal-based catalysts: Pt, Rh, Rh/gamma-Al2O3, Rh-Ce, and Rh-Ce/gamma-Al2O3, as a function of carbon-to-oxygen feed ratio. The Rh-Ce/gamma-Al2O3 catalyst exhibited the highest feedstock conversion as well as selectivities to both synthesis gas and hydrocarbon products (lowest selectivities to H2O and CO2). Experimental results demonstrate a high stability of aromatic rings within the reactor system. Benzene and toluene seem to react primarily heterogeneously, producing only syngas and combustion products. Ethylbenzene and cumene behaved similarly, with higher conversions than benzene and toluene, and high product selectivity to styrene, likely due to homogeneous reactions involving their alkyl groups. Styrene exhibited low conversions over Rh-Ce/gamma-Al2O3, emphasizing the stability of styrene in the reactor system. (C) 2009 American Institute of Chemical Engineers AIChE. J, 56: 979-988. 2010