The hydrogen adsorption on carbon nanofibers of different origin was investigated by thermogravimetric measurements at temperatures between -10 and 25 degreesC and pressures up to 140 bar. The applied gravimetric apparatus yields a distinctly higher precision, compared to volumetric and calorimetric methods. All investigated carbon nanofibers show a hydrogen uptake below 0.3 wt.% independently from sample pretreatment. (C) 2004 Elsevier B.V. All rights reserved.