We have calculated the electronic band structure of the Tc = 85 K phase of Bi2Sr2CaCu2O8 using atomic coordinates derived from x-ray diffraction measurements. Bands arising from hybridized Cu-3d/0-2p and Bi-6p/0-2p orbitals intersect the Fermi level. The relative prominence of the Bi-O conduction bands is sensitive to the arrangement of the O atoms in the Bi-O intergrowth regions, as demonstrated by calculations based on an alternate Bi2O2 sub-structure. Assuming Tc is density-of-states driven, our studies suggest that enhanced values of Tc could arise from such alternate sub-structures, either in the form of structural defects or separate phases, as well as from triple perovskite layers. © 1988 Elsevier Science Publishers B.V.