Magnesium is the fourth most abundant metal found in the body. It plays a crucial role in numerous biological processes. It is a natural calcium blocker. It can block or compete with Ca2+ at voltage-dependent, receptor- or leak-operated channels and result in translocation of intracellular Ca2+. Mg2+ inhibits Ca2+ release from the sarcoplasmic reticulum. Intracellular Mg2+ is thought to modulate smooth muscle contractions and the rate of relaxation. Mg2+ is a cofactor of numerous enzymes and is coupled with cellular use of phosphate as an activator and energy source. cAMP-dependent protein and adenylate cyclase are among many enzymes that require Mg2+ for their function. Mg2+ has been used successfully in treating asthma. There is experimental evidence that Mg2+ is required for various immune responses, and in rats, Mg2+ treatment has been shown to attenuate chemically induced pulmonary hypertension. It is not clear if Mg2+ deficiency plays a role in development of some of these diseases, but Mg2+ salts appear to have therapeutic value and certainly it has a role as an adjunct to traditional therapy in various lung diseases.