The cosmic ray spectral variations and anisotropy near Earth during the March 24, 1991, Forbush decrease were evaluated on the basis of neutron monitor data using the technique developed for the analysis of solar cosmic ray ground level enhancements. Evidence was found that the unusual short-term increase just prior to the onset of the global decrease was due to an anisotropic flux of GV particles arriving from the local dusk-midnight sector (GSE latitude: -1¿, GSE longitude: 140 ¿E) which are associated with the powerful interplanetary shock that struck the Earth's magnetosphere at 0342 UT on March 24, 1991. During the main phase of the event the cosmic ray anisotropy vectors exhibited a rotational behavior similar to the typical rotation of the magnetic field vector which is observed when a magnetic cloud is traversed. The study demonstrates the potential of neutron monitor data to provide information about complex transient structures in the near-Earth interplanetary medium. ¿ 2000 American Geophysical Union