Natural gas can be used as a vehicular fuel, but its low energy density is a significant drawback. The energy density can be increased by adsorption of the natural gas on high surface area sorbents. The adsorption of methane on activated carbons and molecular sieves was investigated at pressures up to 16 MPa (2300 psig). The improvement in methane storage capacity over empty cylinders is appreciable at low pressures but diminishes as the pressure increases. When adsorbed, for example, on 9LXC activated carbon at 3, 7, and 14 MPa the energy density increased by 245%, 100%, and 53%, respectively. Less improvement was observed with molecular sieves.