The photodissociation of CH3Cl is an important source of atmospheric chlorine atoms. To more fully understand this reaction, potential energy surfaces of the ground state X(1)A' and the first two excited singlets (2(1)A' and 1(1)A '', corresponding to the degenerate E-1 at the ground state C-3 nu equilibrium geometry) of CH3Cl have been constructed through ab initio Complete Active Space SCF calculations. AX(1)A'/2(1)A' conical intersection was located, and the importance of this feature in the photolysis of the C-H bond after photoexcitation at 193 nm is discussed. (C) 2010 Elsevier B.V. All rights reserved.