Equilibrium adsorption data are reported for methane, ethane, and ethylene on titanosilicate ETS-10 zeolite for pressures up to 1000 kPa and temperatures of (280, 300, 315, 325, and 350) K. The data are modeled using Toth, unilan, and virial three-constant isotherms. Unconstrained and constrained optimization techniques have been applied to derive the model parameters. Henry's constant and limiting enthalpies of adsorption are deduced from the virial three-constant model and compared to the values derived for the Toth and unilan models. The saturation concentration is deduced on the basis of the assumption of 95% occupancy of the free zeolite voidage with adsorbed-state molecular volumes estimated from liquid densities.