  In principle, leading neutrons produced in photoproduction and deep-inelastic
scattering at HERA have the potential to determine the pion structure function,
the neutron absorptive cross section and the form of the pion flux. To explore
this potential we compare theoretical predictions for the x_L and p_t spectra
of leading neutrons, and the Q^2 dependence of the cross section, with the
existing ZEUS data.
