Precise energy eigenvalues of doubly excited D-1,3(o) states originating from 2pnd (n = 3-8) configuration of two-electron atoms (Z = 3-7) have been calculated by using Ritz variational method in Hylleraas coordinates. Except for a few, the present non-relativistic energy values are the lowest yet obtained. The energy eigenvalues of a number of these states are being reported for the first time. Comparisons with existing experimental results are also made. The effective quantum numbers (n*) for the states mentioned above have been calculated using the theory of quantum defect. Crown Copyright (C) 2009 Published by Elsevier B. V. All rights reserved.