The treatment of kaon decays using chiral symmetry yields predictions for thè form factors in K→ππeν. In addition, the large-Nc limit of QCD implies that a particular combination of low-energy constants should be suppressed. We present the chiral predictions for Kl4 decays at next-to-leading order in the energy expansion. By combining the phenomenologies of Kl4 and ππ scattering, we test these predictions and provide a determination of the parameters in the chiral Lagrangian of QCD.