In the present work, design and operation of a high pressure gas adsorption apparatus at room temperature and at pressures up to 100 bar are discussed. A theoretical and experimental error analysis is done to determine accuracy and robustness of the measurements. For this study, activated carbon was selected as the adsorbent and hydrogen as the adsorbate gas. A sensitivity analysis was done by taking into account the effects of temperature, pressure, volume and weight of the sample. The analysis shows that the volumes of the sample and reference cells as determined by helium-free space measurements have significant effect on the accuracy of the adsorption uptake measurement. For instance, a 0.1% error in the measurement of either volume led to approximately a 3% error in hydrogen uptake measurement at 298 K and 100 bar. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.