Measurements of diffractive phenomena observed at HERA and the Tevatron
are reviewed. A short introduction to the theoretical background is
presented where colour singlet exchange reactions are discussed
and the diffractive contribution and its interpretation
via pomeron exchange outlined.
The review focuses on the current experimental directions at HERA and
discusses exclusive production of vector mesons, the dissociation of
real photons and the deep inelastic structure of diffraction.
Complementary
information obtained from hadronic final states and jet structures
is also discussed.
The experimental signatures for diffractive jet and
production
observed at the Tevatron are described and the rates compared with those
from the HERA experiments.
Talk presented at the 25th SLAC Summer Institute,
SLAC, August 1997.
December 1997