The charge distribution in linear pentaiodide ions of D∞h symmetry has been calculated by using a five-centre six-electron bonding scheme involving the iodine 5pσ orbitals. This is an extension of the three- centre four-electron scheme which accounts well for the values of the nuclear quadrupole coupling constants for trihalide ion and amine- halogen complexes. It has recently been shown that the amylose-iodine complex may contain linear I5- ions, and it is shown in the present work that the five-centre six-electron bonding scheme accounts well for the values of the quadrupole coupling constants obtained from the iodine- 129 Mossbauer spectrum of this complex.