A consistent set of ab initio-based kinetic and thermodynamic data is applied for the simulation of an ethane steam cracking furnace. The thermodynamic data are calculated using accurate quantum chemical CBS-QB3 calculations including corrections for hindered internal rotation. The kinetics are obtained from CBS-QB3-based group additive models. With these thermodynamic and kinetic data, simulations for pilot and industrial ethane steam cracking reactors over a wide range of process conditions are performed. It is shown that, without adjusting any parameter, the main product yields can be predicted within 15% rel. of the experimentally observed cracking yields. This indicates the tremendous potential of integrating ab initio methods with engineering models for accurate reactor simulations. (C) 2010 American Institute of Chemical Engineers AIChE J, 57: 482-496, 2011