It is well established that magnesium has a considerable potential for use as a biodegradable material. This report describes the effect of processing by severe plastic deformation (SPD) on the grain refinement, mechanical behavior, biocompatibility and corrosion behavior of commercial purity magnesium. The material was received as cast slabs and processed by rolling, equal-channel angular pressing and high-pressure torsion to produce samples with average grain sizes in the range of similar to 0.5-300 mu m. The results show that severe plastic deformation does not affect the biocompatibility. However, the corrosion behavior is affected by the processing route. Specifically, SPD processing leads to general corrosion as opposed to localized corrosion in the as-cast and hot-rolled condition.