The "N-NMR spectra of vitamin B12 analogues obtained in fully "N-labelled form have been measured by direct and inverse (15N,lH) correlated spectroscopy. All resonances, except those of the NH, groups, have been assigned to individual N-atoms. The influences on 6(N) are analyzed and discussed which are caused by changing the B-face ligand from CN to H 2 0 or CH3 and by switching the a -face ligand from the base-on to the base-off state. An implication of the correct resonance assignment on biosynthetic pathways is demonstrated.