A novel magnetoplethysmogram (MPG) system is designed and developed for the real time, noninvasive monitoring of hemoglobin concentration in arterial blood. The basic principle of modulated magnetic signature of blood (MMSB), is validated with clinical trial. The MPG probe consists of a permanent magnet and a Giant Magneto Resistance (GMR) sensor. A strap and stand design enable reliable capture of continuous cycles of MPG with relative ease. Clinical validation with data from 64 patients carried out at the institute hospital of IIT Madras, using the proposed system gave a worst-case error of 6.5% in the measurement of hemoglobin concentration in arterial blood. Linear regression analysis using least square method, exhibited a standard deviation of 0.64 g/dL. Results from the clinical validation establish the practicability of the proffered MPG system. © 2001-2012 IEEE.