The ferroelastic and ferroelectric properties of KCN crystals were investigated through the EPR spectra of HCN- and N2 molecular ions in the lattice. The domain structure generated by the cubic → oethorhombic transition at 168 K consist of six non equivalent domain orientations. The analysis of the HCN- spectra between 83 K and 170 K showed that reorientations of the CN- ions occurs between the [100] and < 111 > orthorhombic directions, which have a minimum elastic energy 7.4 meV higher than the [100]. Based on a simple mode1 Hamiltonian in which the interactions between the CN- ions are of an electrostatic dipole-dipole nature, we showed that the ordered phase consist of an antiferroelectric state