1. NAD+ kinase (ATP:NAD+ 2' phosphotransferase, EC 184.108.40.206) has been purified to apparent enzymic homogeneity on Blue Sepharose CL-6B. 2. The molecular weight of the active species is about 260,000 as determined by PAGE and gel chromatography. Protein staining (PAGE) revealed minor bands with molecular weight values of 40,000, 140,000 and 550,000. Subunit studies (SDS-PAGE) gave evidence of a single band of molecular weight approximately 32,000. 3. On the basis of the release patterns of this enzyme from several affinity gels, an elution diagram is proposed as a device to assess the contribution of any of the several displacing agents that can be used to manipulate the desorption of a (enzyme) ligate from an immobilized ligand.