This book critically summarizes the effects of various suitable alloying elements and particulate reinforcements on mechanical and degradation properties of pure Mg and Mg alloys targeting biomedical applications. The suitability of alloying elements and particulate reinforcements are discussed based on their levels of toxic effects on human body. First attempt is made to study and discuss on the various available synthesizing techniques for fabrication of both impermeable and porous Mg materials. Further, more emphasis on development of new magnesium matrix nanocomposites (MMNC) is made owing to the similarities between natural bone and MMNCs as bio-“nanocomposite”. The information on synthesis, toxicity of alloying elements and reinforcements and their effects on mechanical and degradation properties of pure Mg will enable the researchers to effectively design Mg alloys and composites targeting biomedical applications.