To extract information on the rotational population distributions of the methyl radical from photodissociation by the 2+1 resonance-enhanced multiphoton ionization technique, its rotational line strength formulas of the two-photon transitions have been reexamined. Symmetry-adapted rovibronic-nuclear spin wave functions of CH3 and CD3 in the \(X) over tilde (2)A(2)(')> and \np (2)A(2)(')> electronic states were utilized in the derivation. Transformation properties of the rovibronic and nuclear spin basis functions under the permutation-inversion group D-3h(M) have been employed to construct the total wave functions which follow the appropriate statistics of CH3 and CD3, respectively. Explicit expressions of the two-photon rotational line strengths of the v(2)-active vibronic bands of the methyl radical were reported. (C) 2003 American Institute of Physics.