AbstractThis paper examines the effect of fusing a small carbocyclic ring onto the ortho positions of an aromatic nucleus. Benzene derivatives are considered to which have been fused one, two or three small rings. The effect of varying the size and orientation of the rings is discussed with respect to changes in the σ‐ and π‐bonding networks, the geometry of these molecules and their chemical reactivity. Other aromatic nuclei, such as pyridine, thiophene, naphthalene and the tropylium ion, are also described. Variations in physical properties appear to be best explained by a rehybridization theory which functions in the plane of the system. Perturbations of the π‐bonding framework are better manifested by changes in chemical re