Three/two-photon resonant multiphoton ionization (MPI) of the CH₃I monomer has been studied in the gas phase at 532 and 355nm using time-of-flight mass spectrometry. Under low laser intensity (~10⁹W/cm²) the mass spectra showed peaks at m/z15, 127 and 142, corresponding to [CH₃]⁺, [I]þand [CH₃I]⁺ species, at both these wavelengths. The laser power dependence for [CH₃I]⁺, [I]⁺ and [CH₃]⁺ ions showed a three-photon dependence at 532nm. For the same three ions, photoionization studies at 355nm gave a power dependence of 2. Both these results suggest that a vibronic energy level at ~7_eV, lying in the Rydberg C state, acts as a resonant intermediate level in ionization of CH₃ I. In the case of 355nm, with increasing intensity additional peaks at m/z 139 and 141 were observed which could be assigned to [CI]⁺ and [CH₂I]⁺ fragments. In contrast, for high intensity radiation at 532nm (~2×10¹⁰W/cm²), only the [CI]⁺ fragment was observed. At these wavelengths,fragment ions observed in mass spectra mainly arise from photodissociation of the parent ion.Experiments at another wavelength in the visible region (564.2nm) confirmed the results obtained at 532nm. In order to assess the role of the A ̃state in these MPI experiments, additional experi-ments were performed at 266 and 282.1nm, which access the A state directly via a one-photon  tran-sition, and showed absence of a surviving precursor ion. Reaction energies for various possible dissociation channels of CH₃I/[CH₃I]⁺/[CH₂I]⁺ were calculated theoretically at the MP2 level using the GAMESS electronic structure program.