An electron paramagnetic resonance (EPR) characterization study of isotopically enriched 12C diamond grown by General Electric has been carried out. While other commonly used techniques detect no nitrogen in this diamond, the clear EPR spectrum consistently measured a nitrogen concentration of about 0.05 ppm by calibration against a few standards. The concentration is about 2 orders of magnitude lower than that of a few natural IIa diamonds and over 4 orders of magnitude smaller than that of a typical yellow Ib diamond. The 12C diamond is evaluated to be ideal for research of diamonds under high pressure as well as irradiated diamonds. Both the experimental line shape and second moment do not support a random nitrogen distribution in this diamond. Instead, we found that nitrogen atoms tend to stay apart from one another. This uniformly dispersed nitrogen distribution is a new state of nitrogen found in diamond. © 1994 American Institute of Physics.