Experimental and theoretical studies were reported on equilibrium isotherms of pure methane and ethane adsorption on 4A molecular sieve zeolite at 301 K. The experimental equilibria data were measured using the constantvolume method. The Langmuir, the Freundlich, and BET equations were used to fit the pure component experimental data. The results show that both the Langmuir and Freundlich equations correlated the pure component experimental data fairly well with a correlation coefficient of 0.998 and 0.977 for methane and ethane, respectively. The results of this study showed that ethane was more selectively adsorbed than methane on 4A molecular sieve zeolite.