  Basic physics concepts of the QGSJET model are discussed, starting from the
general picture of high energy hadronic interactions and addressing in some
detail the treatment of multiple scattering processes, contributions of
``soft'' and ``semihard'' parton dynamics, implementation of non-linear
interaction effects. The predictions of the new model version (QGSJET II.03)
are compared to selected accelerator data. Future developments are outlined and
the expected input from the LHC collider for constraining model predictions is
discussed.
