The demonstration of NO formation (1989) by an enzyme in vascular endothelial cells has led to new extensive biological research. The existing methods of NO detection are usually indirect, complicated, and/or insensitive to low levels of NO. The need for a simple, direct method for NO measurement prompted this study. We conbined the spin trap and EPR techniques to measure gaseous NO. Sodium N-methyl-D-glucamine dithiocarbamate (MGD) was synthesized. The spin trap reagent for trapping NO was the [(MGD)2-Fe2+] complex. Sources of NO included saturated NO solution or commercially available NO donor - DEA/NO. Calibrations of NO were made.