The reaction of atomic carbon with N-methylpyrrole, 5b, at 77 K generates the N-methyl-3-dehydropyridinium ylid, 6b, which can be trapped with added hydrogen halides or CO2. The addition of CO2 is strong evidence for the ylid 6b rather than cumulene 7. Deuterium and C-13 labeling studies demonstrate that 6b rapidly rearranges to the N-methyl-2-dehydropyridinium ylid, 13, by an intermolecular mechanism. Ylid 13 can be trapped with added acids or with O-2 to form 1-methyl-2-pyridone.