This paper describes an experimental search for GUT magnetic monopoles in the
MACRO experiment using the nuclear track subdetector CR39. After discussing the
working principle, the charge resolution and the calibration of the detector,
the experimental procedure for searching for magnetic monopoles is described.
Since no candidates were found, the upper flux limits obtained by the MACRO
CR39 used as a "stand alone detector" for magnetic monopoles of different
magnetic charges are presented.Comment: 4 pages, 7 EPS figures included with epsfig, uses espcrc2.sty Talk
given at the Sixth Topical Seminar on Neutrino and Astroparticle Physics, San
Miniato, Italy, 17-21 May 199