  The theoretical motivation for exotic stable massive particles (SMPs) and the
results of SMP searches at non-collider facilities are reviewed. SMPs are
defined such that they would be sufficiently long-lived so as to still exist in
the cosmos either as Big Bang relics or secondary collision products, and
sufficiently massive to be beyond the reach of any conceivable
accelerator-based experiment. The discovery of SMPs would address a number of
important questions in modern physics, such as the origin and composition of
dark matter in the Universe and the unification of the fundamental forces. This
review outlines the scenarios predicting SMPs and the techniques used at
non-collider experiments to look for SMPs, eg in cosmic rays and bound in
matter. The limits so far obtained on the fluxes and matter densities of SMPs
which possess various detection-relevant properties such as electric and
magnetic charge are given.
