[en] A general decomposition of the amplitudes for the 2 → 2 processes γν → γν and γγ → ν bar ν is obtained using gauge invariance and Bose symmetry. The restrictions implied by this decomposition are investigated for the reaction γγ → ν bar ν by computing the one-loop helicity amplitudes in the standard model. In the center of mass, where √s = 2ω, the cross section grows roughly as ω⁶ up to the threshold for W-boson production, √s 2m_W. Astrophysical implications of very high energy photon-neutrino interactions are discussed