Photochemistry of p-toluidine was investigated by matrix-isolation infrared (IR) spectroscopy and density functional theory (DFT). Its photo-produced intermediate is identified as 4-methylanilino radical, which recombines with a photodissociated hydrogen atom to reproduce p-toluidine or a final photoproduct in an annealing procedure at 28 K. The final photoproduct is identified as 4-methyl-2,4-cyclohexadiene-1-imine, which has cis and trans conformers with respect to the direction of the hydrogen atom of the imino group. Experimental and theoretical studies confirm that the amino group in p-toluidine has higher photoreactivity than its methyl group. (C) 2005 Elsevier B.V. All rights reserved.