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ALTHOUGH there have been experimental studies of the structure of the C₆₀ molecule in the gas phase¹ and the solid state at low temperature², so far only indirect experimental details of the structure of the C₇₀ molecule have been available³. The ellipsoidal structure for C₇₀, the subject of recent theoretical work^4,5, should provide a useful test of current understanding of carbon–carbon bonding, in that a single molecule contains several distinct types of bond in various relationships to pentagonal and hexagonal rings. Conventional crystallographic techniques are not suitable for studying C₇₀ at room temperature because of poor crystallinity and orientational disorder in solid samples. Here we present the results of a study in which the molecular structure of C₇₀ was deduced from electron diffraction using a simulated-annealing method. The 'rugby' ball structure is confirmed, with a slight pinching of the waist, and …