Recently, particular emphasis has been placed on the problem of sampling gas-charged groundwater such as can be encountered in landfill leachate plumes and natural gas associated formations. Further research is required to realize the goal of quantitative estimation of sampling bias due to volatilization. The present study incorporates several improvements in design over the previous studies. Larger Henry's constant values are represented by the organic contaminants, and methane was included. Dissolved carbon dioxide concentrations were measured in order to establish a link with theory. In addition, the experimental well was constructed of stainless steel instead of PVC, eliminating the possibility sorption losses in the well; the well contained a sampling port at the bottom for obtaining representative control samples. Finally, six samplers were evaluated at two concentration levels, making this a more comprehensive study.