Isospin Violation in 0

162001-1 On the basis of a next-to-leading-order calculation in chiral perturbation theory, the first complete analysis of isospin breaking for direct CP violation in K0 ! 2 decays is performed. We find a destructive interference between three different sources of isospin violation in the CP violation parameter 0. Within the uncertainties of large-Nc estimates for the low-energy constants, the isospin violating correction for 0 is below 15%.