Two-dimensional {110} superlattices have been observed in Bi2(Sr, Ca)3Cu2O8+yby transmission electron microscopy from (001) and (110) planes but not from the (100) plane. Lattice images in the (110) plane show stacking faults intersecting the superlattice. It is possible that the existence of superlattices and stacking faults is important in the formation of Cooper pairs for superconductivity, and that ordered multiphase layered assemblages can be used to produce material of higherTc. Comparisons of ionic radii in a similar material, Tl2Ba2CaCu2O8+y, suggest that the superlattice results from periodic lattice strain modulation.