  In the framework of conventional Regge theory we present a common description
of total photon-proton cross-section and proton structure functions in the
region $0 \leq Q^2 \leq 5 \ {\rm GeV}^2$. Using it as an initial condition in
the perturbative QCD evolution equation, we describe structure functions at any
$Q^2$ and $x$ - including the small $x$ region explored at HERA.
