This paper presents work on hydrogen generation from sodium borohydride (NaBH4) solution that could have great application in micro fuel cells. A hydrogen test method has been developed, which is very effective for sustained measurement of the generation rate and yield of hydrogen. The hydrogen is supplied to a proton exchange membrane fuel cell. The discharged current is measured by a computer-controlled electronic load system connecting to the fuel cell where hydrogen generation rate and yield are calculated. The study is focused on the slow release of hydrogen. The results show that if the concentration of NaBH4 solution is 10%, no solid substance is formed and the catalyst supported on the ion-exchange resin beads remains unchanged. The hydrogen generation can be controlled by inserting or removing the catalyst into/from the solution, which can be applied to a micro fuel cell. When the concentration of NaBH4 solution is 20%, however, the catalyst beads are broken up and dispersed in the solution (probably by the NaBO2 crystallization force and give rise to uncontrollable generation of hydrogen. (c) 2005 Elsevier B.V. All rights reserved.