The electromagnetic and weak structure functions of the photon can be studi
ed in the deep inelastic electron-photon processes e gamma --> e + X and e
gamma --> nu + X. While at low energies only virtual photon exchange is ope
rative in the neutral-current process, additional Z-exchange becomes releva
nt for high Q(2) of order M-Z(2) at e(+)e(-) linear colliders. Likewise the
charged-current process can be observed at these high energy colliders. By
measuring the electroweak neutral- and charged-current structure functions
, the up- and down-type quark content of the photon can be determined separ
ately. (C) 1999 Elsevier Science B.V. All rights reserved.