Supercritical water gasification of crude glycerol for hydrogen (H-2) production is one possible use of crude glycerol from biodiesel production. In this study, a series of central composite designed experiments were conducted to investigate the reforming of crude glycerol for producing a H-2 rich gas. A mathematical model defining the effect of glycerol concentration, reaction temperature and KOH concentration was developed with response surface methodology and was used to improve the H-2 yield. The study revealed that the optimum reaction conditions for producing H-2 were 500 degrees C, 7wt.% glycerol concentration and 2.39molL(-1) KOH concentration. The corresponding pressure was 45MPa. Under these optimized reaction conditions, the H-2 mole fraction yield in the gaseous product was 27.9 +/- 0.22mol%. The mole fraction yields of other gas products (CH4, CO and CO2) were small compared to that of H-2. Copyright (c) 2012 John Wiley & Sons, Ltd.