Optically pure 5,6-dimethylidenebicyclo[2.2.1]hept-2-yl derivatives have been prepared. The sign of the Cotton effects associated with lowest-energy transition of 2-(dicyanomethylidene)-((-)-(1S,4S)-15), (E)-2-(methoxyimino)-((+)-(1S,4S)-16), (Z)-2-(methoxyimino)-5,6-dimethylidenebicyclo[2.2.1]heptane ((-)(1S,4S)-17), and 2,3,5-trimethylidenebicyclo[2.2.1]heptane ((-)-(1R,4S)-18) is opposite to the chirality constituted by the coupling of the electric transition moments of the two homoconjugated -chromophores (Kuhn-Kirkwood dipole-coupling mechanism). When the substituents at C(2) are not -functions, no general rule can be retained for the chiroptical properties of the 5,6-dimethylidenebicyclo[2.2.1]hept-2-yl systems as shown for dimethyl acetal (-)-(1S,4S)-19, ethylene acetal (+)-(1R,4R)-20, exo and endo methyl ethers (+)-(1R,2S,4R)-21 and (+)-(1R,2R,4R)-22, and for spirol[5,6-dimethylidenebicyclo[2.2.1]heptane-2.2'-oxiranes](-)-(1S,2S,4S)-23 and (-)-(1S,2S,4S)-24.