We present molecular simulation results of solubility and self-diffusion of carbon dioxide and hydrogen sulfide in linear polyethylene melts. Simulations were carried out at 433 K and pressures in the range 0.1-10 MPa. Solubilities were computed using Monte Carlo simulations in the osmotic ensemble, with constant number of polymer chains, pressure, temperature and gases chemical potential. Diffusion coefficients were obtained from equilibrium molecular dynamics. It is found that hydrogen sulfide has a higher solubility in polyethylene than carbon dioxide at a given pressure. Self-diffusion coefficients are found to slightly increase with increasing penetrant weight fraction. (c) 2007 Elsevier B.V. All rights reserved.