  Recent theoretical developments to calculate cross sections of hadronic
objects in the high energy limit are summarised and experimental attempts to
establish the need for new QCD effects connected with a resummation of small
hadron momentum fractions x are reviewed.
  The relation between small-$x$ parton dynamics and the phenomenon of
diffraction is briefly out-lined. In addition, a search for a novel,
non-perturbative QCD effect, the production of QCD instanton induced events, is
presented.
