The transmission of polar effects through the bicyclo[2.2.2] octane framework has been investigated by ascertaining how the geometry of a phenyl group at a bridgehead position is affected by a variable substituent at the opposite bridgehead position. We have determined the molecular structure of several Ph-C(CH2CH2) C-3-X molecules (where X is a charged or dipolar substituent) from HF/6-31G* and B3LYP/6-311++ G** molecular orbital calculations and have progressively replaced each of the three -CH2-CH2-bridges by a pair of hydrogen atoms. Thus the bicyclo[2.2.2] octane derivatives were changed first into cyclohexane derivatives in the boat conformation, then into n-butane derivatives in the anti-syn-anti conformation, and eventually into assemblies of two molecules, Ph-CH3 and CH3-X, appropriately oriented and kept at a fixed distance. For each variable substituent the deformation of the benzene ring relative to X) H remains substantially the same even when the substituent and the phenyl group are no longer connected by covalent bonds. This provides unequivocal evidence that long-range polar effects in bicyclo[2.2.2] octane derivatives are actually field effects, being transmitted through space rather than through bonds. Varying the substituent X in a series of Ph-C(CH2-CH2) 3C-X molecules gives rise to geometrical variation (relative to X) H) not only in the benzene ring but also in the bicyclo[2.2.2] octane cage. The two deformations are poorly correlated. The rather small deformation of the benzene ring correlates well with traditional measures of long-range polar effects in bicyclo[2.2.2] octane derivatives, such as sigma(F) or sigma(I) values. The much larger deformation of the bicyclo[2.2.2] octane cage is controlled primarily by the electronegativity of X, similar to deformation of the benzene ring in Ph-X molecules. Thus the field and electronegativity effects of the substituent are well separated and can be studied simultaneously, as they act on different parts of the molecular skeleton.