Natural gas vehicles (NGV) have attracted more and more attention from policy makers since natural gas is a clean substitute for traditional fossil fuel that is also readily accessible. In some areas such as the state of Texas, vehicles that do not use traditional fossil fuel (e.g., NGVs) are exempt from paying fuel taxes. Government financial incentives have motivated substantial adoption of NGVs. This paper studies NGV adoption behavior in both U.S. and Texas markets to estimate the dynamics of NGV diffusion. This research employs well-known Bass diffusion models applied to NGV adoption, using data from both the U.S. and Texas. Among several interesting results, we find that NGV adoption through an imitation effect appears to be significant for the U.S. NGV market.