Microscopic reaction pathways for the transformation of chemisorbed methyl to atomic carbon on Pt{110}(1 x 2) have been identified using calculations based on density functional theory in combination with a constrained minimization technique. For CH3 and CH2 dehydrogenation, calculated activation energies of 0.34 eV (33 kJ mol(-1)) and 0.56 eV (54 U mol(-1)) are obtained, respectively. For CH dehydrogenation, the calculated activation barrier of 1.20 eV (116 kJ mol(-1)) is in excellent agreement with the experimentally determined barrier of 1.25 eV (121 +/- 3 kJ mol(-1)).(1) The resulting calculated reaction-energy profile for the conversion of CH3 to CH and ultimately carbon on Pt{110}(1 x 2) is reported and discussed in terms of previous experimental results obtained for this system.