  Using Chiral Perturbation Theory at one-loop we analyze the consequences of
twisted boundary conditions. We point out that due to the broken Lorentz and
reflection symmetry a number of unexpected terms show up in the expressions. We
explicitly discuss the pseudo-scalar octet masses, axial-vector and
pseudo-scalar decay constants and electromagnetic form-factors. We show how the
Ward identities are satisfied using the momentum dependent masses and the
non-zero vacuum-expectation-values values for the electromagnetic (vector)
currents. Explicit expressions at one-loop are provided and an appendix
discusses the needed one-loop twisted finite volume integrals.
