  The strong isospin-breaking correction, Omega_{st}, which appears in
estimates of the Standard Model value for the direct CP-violating ratio
epsilon'/epsilon, is evaluated to next-to-leading order (NLO) in the chiral
expansion using Chiral Perturbation Theory. The relevant linear combinations of
the unknown NLO CP-odd weak low-energy constants (LEC's) which, in combination
with 1-loop and strong LEC contributions, are required for a complete
determination at this order, are estimated using two different models. It is
found that, to NLO, Omega_{st}=0.08 +/- 0.05, significantly reduced from the
``standard'' value, 0.25 +/- 0.08, employed in recent analyses. The potentially
significant numerical impact of this decrease on Standard Model predictions for
epsilon'/epsilon, associated with the decreased cancellation between gluonic
penguin and electroweak penguin contributions, is also discussed.
