  The search for magnetic monopoles in the cosmic radiation remains one of the
main aims of non-accelerator particle astrophysics. Experiments at high
altitude allow lower mass thresholds with respect to detectors at sea level or
underground. The SLIM experiment is a large array of nuclear track detectors at
the Chacaltaya High Altitude Laboratory (5290 m a.s.l.). The results from the
analysis of 171 m$^2$ exposed for more than 3.5 y are here reported. The
completion of the analysis of the whole detector will allow to set the lowest
flux upper limit for Magnetic Monopoles in the mass range 10$^5$ - 10$^{12}$
GeV. The experiment is also sensitive to SQM nuggets and Q-balls, which are
possible Dark Matter candidates.
