A free radical mechanism for the thermolysis of N,N′-diacetyl tetrahydrodipyridyl (1) to pyridine, 4-acetyl pyridine (2) and to (4-pyridine)-l ethanol acetate (3) is proposed. Both chemical evidence (incorporation of pyridine and of 4-acetyl pyridine in the acetate (3) and physical evidence (observation of the free pyridinyl radical araising from homolytic cleavage of dimer 1, spin trapping of the