Calculations have been made of average rotational state populations or probabilities for bonds in polyethylene oxide (PEO) chains, taking account of the interdependence of bond rotational potential functions by using methods developed by Flory and co-workers. These are based on the rotational isomeric state model and have a formal similarity to the techniques used in the problem of the linear Ising model of ferromagnetism. The calculations have been carried out for both chemical types of bond in PEO, for short chains up to 21 monomer units, for longer chains with 136 monomer units (corresponding to PEO of mol. wt. 6000) and for infinite chains. The effect of OH endgroups and temperature variations have been taken into account. The statistical weight parameters used were taken from the literature and were those already successfully employed in theoretical interpretations of stress temperature coefficient and mean square dipole moment measurements of PEO chains.