The major mononuclear aluminum species obtained in the reaction of aluminum atoms with dimethyl sulfide (DMS) and diethyl sulfide (DES), under cryogenic conditions, are the C-S insertion products, CH3AlSCH3 and CH3CH2AlSCH2CH3 , respectively, showing that aluminum atoms can activate C-S bonds. The magnetic parameters were extracted from the EPR spectrum. Support for the spectral assignment was obtained by repeating the experiments with C-13-labeled dimethyl sulfide yielding (CH3AlSCH3)-C-13-C-13 . DFT calculations using the M06 functional have proven to be effective in predicting the isotropic and anisotropic Al hyperfine interaction values of the aluminum atom. C-S insertion products. In addition, the thioalkyl radicals, CH(3)SCH(2)(center dot )and (CH3CH2SCHCH3)-C-center dot were formed in the aluminum atom reaction.