Mechanical alloying is becoming quite common as a method of improving the hydrogen storage properties of metal powders. This is particularly important in magnesium where the sorption, i.e. absorption and desorption rate is quite sluggish. So to imrove the rate to values suitable for practical applications, an efficient method of structural refinement is necessary. In this study various additives are used to aid milling of magnesium powders. Milling is carried out with an attritor, addtives are on a constant volume basis, (5 vol%). Additives investigated in this work, namely SiC, Al 2O 3, V, graphite are chosen so as to cover a wide hardness range. Structural refinement after milling are studied both metallographically and in terms of X-ray profile analysis. It is concluded that for effiecient structural refinement the additive should be chosen not on the basis of its hardness, but rather whether or not it is preserved with an acceptable size during milling. Thus of the addtives investigated in this work graphite and Al 2O 3 are found to be most effective.