A novel technique, using energy dispersive X-ray microanalysis (EXAtm), for noninvasive intracellular (i.c.) measurement of magnesium [Mg2+]i has now been accomplished and proven to be a valuable tool in multiple aspects of normal as well as pathological magnesium metabolism. Since only 1% of total body Mg2+ is found in the intravascular space, serum levels of Mg2+ give little information about a patient's overall Mg2+ status with respect to this essential mineral. Using the EXAtm analysis it has shown been determined that Mg2+ levels are significantly reduced in many physiological states which may lead to serious pathological conditions [15]. Description of the methodology and examples of data as well as potential applications will focus on intracellular (i.c.) [Mg2+]i determinations obtained in cells from subjects with cardiovascular disease (CVD) syndromes related to Mg2+ deficiency. Examples of the application of EXAtm evaluation include examination of intracellular magnesium and other minerals in a wide spectrum of conditions which include cardiovascular conditions, arrhythmias, heart failure, myocardial infarction, and bypass surgery. Standardization of control values were performed at NASA.