a b s t r a c t The Direct Simulation Monte Carlo (DSMC) technique is used here to describe the transition region in Titan's atmosphere where the gas flow goes from being collisional to collisionless. We expand on our pre-vious study (Tucker, O. by including H 2 in addi-tion to CH 4 and N 2 . We again find that thermal escape of CH 4 is Jeans-like, contrary to what has been suggested by some fluid/continuum models. However, we also show that the temperature of molecular hydrogen separates from the background gas well below the exobase, and its escape cools the back-ground gas. This results in a non-isothermal CH 4 density profile without requiring an upward CH 4 flux and, therefore, fits using the diffusion equation can overestimate the escape flux. These simulations also reproduce the Cassini H 2 density versus altitude data averaged over flybys for which Titan is orbiting in Saturn's plasma sheet, but with a somewhat different escape rate than suggested by the diffusion equa-tion. However, for flybys for which Titan is not in Saturn's plasma sheet our simulations result in H 2 den-sities that diffusively separate from the N 2 densities at lower altitudes than typically indicated by the Cassini data. By tracking ballistic transport in the H 2 corona we show that a global, as well as temporal description of the exobase region is required. Published by Elsevier Inc.