1. 1. Glucagon (75 μg. per ml.) stimulates the incorporation of [3H]thymidine and [3H]TTP into DNA. 2. 2. Thymidine kinase, thymidine monophosphate nucleotidase, and DNA polymerase are unaffected by pretreatment of liver preparations with glucagon. 3. 3. Evidence is presented for the existence of terminal deoxynucleotidyl transferase activity in foetal rat liver. 4. 4. The development of DNA polymerase and terminal transferase is presented as a function of age. 5. 5. Glucagon stimulation of terminal transferase activity can account for the increase in [3H]dT and [3H]TTP incorporation observed under the influence of the hormone.