  We show that the recent measurements of the total photoproduction cross
section at HERA energies [1] are in agreement with our earlier prediction based
on high-energy hadronic structure of the photon in the QCD minijet-type model
[2]. We discuss an improved calculation of the photoproduction cross section,
in which the soft part, motivated by the Regge theory, is taken to be
energy-dependent and the semi-hard hadronic part is carefully eikonalized to
take into account for the multiple scatterings and to include the appropriate
hadronic probability of the photon [3]. We show that the extrapolation of our
cross section to ultra-high energies, of relevance to the cosmic ray physics,
gives significant contribution to the ``conventional'' value, but cannot
account for the anomalous muon content observed in the cosmic ray air-showers
associated with astrophysical point sources [4]. (invited talk presented at QCD
Recontres de Moriond 1993)
