Selective detection of (1-13C)-glucose and its glycolytic product, (3-13C)-lactate, was achieved by selective 13C NMR spectroscopy with 1H cross polarization. The total sensitivity of conventional broadband experiments was retained, and peak intensities were at least equivalent to those obtained with the inverse detection technique (i.e., 1H(13C)) for single proton resonances. A key advantage of the method is that it maintains the specific absorption rate (SAR) within FDA limits of 5 W/kg by reducing power deposition during decoupling. In this study we have monitored the kinetics of metabolism of 13C-labeled glucose to lactate following intravenous infusion of 0.55 ml of 0.18 M labeled glucose. Physiological effects were minimized by a) maintaining total plasma glucose concentrations below 20 mM throughout the course of NMR experiment and b) by avoiding significant heating of the tumor.