Search for supermassive magnetic monopoles with the MACRO detector at the Gran Sasso Laboratory

We present the results of the search for supermassive magnetic monopoles with the MACRO experiment. Our detector is equipped with three independent subdetectors (liquid scintillation counters, limited streamer tubes and nuclear track detectors), operating in different ranges of monopole velocity. In several years of data taking no candidates were found; the present flux upper limits are at the level of half the Parker Bound for β > 10-4; for 10-4 < β < 5 x 10-2 the limit is the best existing