Supermassive magnetic monopoles are an inevitable consequence of all Grand Unified Theories (GUT‘s). They would have originated in the very hot early universe some 10-35sec, after the Big Bang when the unified force split apart into the strong and electroweak forces. Over thirty laboratories throughout the world have constructed or are presently constructing detectors to search for such primordial monopoles in cosmic rays. This paper, partly tutorial, reviews the past monopole detector work at IBM and describes the present effort to set-up at the Brookhaven National Laboratory a large-area superconducting induciion detector. Two detectors are being built based upon the high-order gradiometer, fully coincident, closed-box design previously developed at IBM. The first, utilizing an existing magnet-testing dewar at BNL, is a rectangular parallelopiped detector of 1.0 m2 effective area (averaged over 4π sr for isotropic flux) being built to test the feasibility of large area schemes in preparation for construction of a much larger 4.0 m2 octagonal prism detector. The latter could serve as the prototype for an array of detectors to reach the Parker bound on monopole flux set by the existence of the 3 μG galactic magnetic field in several years of operation. © 1987 IEEE.