$K\to 3\pi$ Decays in Chiral Perturbation Theory

The CP conserving amplitudes for the decays $K\to 3\pi$ are calculated in Chiral Perturbation Theory at the next-to-leading order. We present the expressions in a compact form with single parameter functions only. These expressions are then fitted to all available $K\to 2\pi$ and $K\to 3\pi$ data to obtain a fit of the parameters that occur. We compare with the work of Kambor, Missimer and Wyler.