1. Six nucleoside-nucleotide phosphotransferases A-F were isolated from chromatin of Morris Hepatoma 9121 cells and characterized. 2. The apparent mol wt are: 13,000 daltons for A, 35,000 or 70,000 for B and E, 240,000 for C, 180,000 for D and 300,000-400,000 for F. 3. The sedimentation values are: 2.5-3 S for A, 3 or 5 S for B and E, 11 S for C, 7-8 S for D and 14 S for F. 4. The activity of the six enzymes A-F was stimulated with 1-2.5 micrograms calf thymus DNA using thymidine/ATP as substrates. 5. In the presence of defined polydeoxynucleotides, each enzyme A-F showed a differential preference for its substrates.