6-Aminofulvene-2-aldimines are easily prepared as yellow or red crystalline compounds from 6-di-methylaminofulvene. A study of their physical properties shows that in these systems an intramolecular hydrogen bond exists, through which a very fast tautomeric proton exchange takes place. From the physical evidence it is deduced that nonclassical aromaticity due to delocalization of electrons through the hydrogen bond does not exist in these and related systems. © 1970, American Chemical Society. All rights reserved.