Supersonic molecular beams have been used to study methane dissociative adsorption on Pt{110}(1 x 2) at incident translational energies of 20 to 700 meV, incident vibrational temperatures of 300 to 800 K and surface temperatures from 400 to 1000 K. At E(t)less than or equal to 100 meV, the initial dissociative sticking probability, s(0), rises sharply. The process is facilitated by vibrational excitation of the deformation modes and surface temperature. At E-t> 100 meV, an activated adsorption process becomes dominant, with an activation barrier of similar to 146 meV. At E(t)greater than or equal to 230 meV, s(0) attains a limiting value which is strongly enhanced by excitation of the C-H stretch modes in the incident molecule. An increase in the surface temperature also enhances s(0), at all incident translational energies. The mechanistic implications are discussed and it is concluded that the low translational energy process is a distinctive steering-assisted direct adsorption pathway. (C) 2000 American Institute of Physics. [S0021-9606(00)00510-9].