The dipole moments of 13 derivatives of 4-pyridone were measured. Attempts to obtain a value for 4-pyridone were unsuccessful but a value of 6.O D is compatible with other evidence. Dipole moment and n.m.r, evidence indicated that for N-phenyl-4-pyridone the phenyl group is inductively electron-repelling (in contrast to that reported)1,2 for N-phenylpyrrole) and that the rings are probably collinear.