It was recently shown that the requirement of invariance under CP and charge symmetry results in a parity conserving pi -N interaction. The neutral pion and charged pion interactions were treated separately. An investigation was made to establish whether or not non-linear (in the pion field) interactions are also parity conserving. The non-linear n-p interaction becomes parity conserving under the requirements of CP invariance and charge symmetry. The general n-n and p-p parity violating, non-linear interaction Lagrangian (with scalar and pseudoscalar couplings only) becomes, as in the linear case, parity conserving. The requirement of charge symmetry, in this case, serves to relate the coupling constants; thus, both linear and non-linear pion interactions are permitted with fermion isotopic doublets. (B.O.G.)