The electrophilic addition of bromine to dibromohomobenzonorbornadiene derivatives at -45 +/- 5degreesC led to the formation of the rearranged and non-rearranged tetrabromides in a ratio of 6:4. However, high-temperature bromination of the same system in CCl4 at 77degreesC produced only non-rearranged products. The formation mechanism of the isomers and the role of the substituent on the rearrangement is discussed. The structure elucidation of the isomeric tetrabromides was achieved from NMR spectral data. The agreement between the calculated dihedral angles and the measured coupling constants is especially excellent. The),gauche effect is discussed. Copyright (C) 2004 John Wiley Sons, Ltd.