N.m.r, data for 14 α,β,β-trimethylstyrenes are given. The aromatic ring shields the β-methyl group cis to it relative to the β-methyl group trans to it. The magnitude of this relative shielding is greatest with ortho-substituted benzene rings. The cisoid homoallylic coupling constants in α,β,β-trimethylstyrenes (and indeed in all examples available from the literature) are smaller than the transoid homoallylic coupling constants.