The hydrogen absorption of sodium intercalated fullerenes (NaxC60) was determined and compared to pure fullerenes (C-60). Up to 3.5 mass% hydrogen can reversibly be absorbed in NaxC60 at 200 degrees C and a hydrogen pressure of 200 bar. The absorbed amount of hydrogen is significantly higher than for the case when only the sodium would be hydrogenated (similar to 1 mass% for x = 10). At 200 bar the onset of hydrogen absorption is observed at 150 degrees C. At a pressure of 1 bar hydrogen the major desorption starts at 250 degrees C and is completed at 300 degrees C (heating rate 1 degrees C min(-1)). This absorption and desorption temperatures are significantly reduced compared to pure C-60, either due to a catalytic reaction of hydrogen on sodium or due to the negatively charged C-60. The hydrogen ab/desorption is accompanied by a partial de/reintercalation of sodium. A minor part of the hydrogen is ionically bonded in NaH and the major part is covalently bonded in C60Hx. The sample can be fully dehydrogenated and no NaH is left after desorption. In contrast to C-60, where the fullerene cages for high hydrogen loadings are destroyed during the sorption process, the NaxC60 sample stays intact. The samples were investigated by X-ray, in-situ neutron powder diffraction and infrared spectroscopy. NaxC60 was synthesized by reacting sodium azide (NaN3) with C-60 (molar ratio of Na:C-60 is 10:1). Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.