  This thesis comprises two investigations, both connected with the attempt to
understand Regge theory in the framework of QCD. The first is about how the
odderon, a Reggeon carrying no charge which is odd under charge conjugation,
couples to the proton. The second concerns unitarity corrections to the BFKL
equation which describes the pomeron, a Reggeon with the quantum numbers of the
vacuum.
  In the first part of this thesis, the odderon exchange contribution to
elastic proton-proton and proton-antiproton scattering is computed. A
geometrical transverse-space model of the proton is constructed to investigate
the influence of a possible diquark cluster in the proton on the odderon-proton
coupling. The average size of this cluster is determined by comparison with
experimental data. Furthermore, the validity of two odderon-proton impact
factors from the literature is tested.
  The second part consists in the derivation of four-pomeron vertices. These
vertices occur in the Generalised Leading Logarithmic Approximation used to
unitarise scattering amplitudes describing the exchange of a perturbative
pomeron. A number of basic functions of which such pomeron vertices are
composed is treated systematically in momentum and position space. Their
conformal transformation properties in impact parameter space are derived. The
vertices are expressed as a number of integrals and cast into the form of
conformally invariant four-point functions.
