2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48380Measurements of neutral current processes off the $Z$-peak are sensitive probes of new interactions, which may be induced by the exchange of new particles such as leptoquarks or extra $Z$'s. This talk reviews the phenomenology of extra interactions in four-fermion processes and updates a global fit to contact terms in the neutral current sector.25 pages, Latex2.09, uses sprocl.sty and psfig.sty, 2 postscript figures. To appear in the Proceedings of the 5th International WEIN Symposium: A Conference on Physics Beyond the Standard Model (WEIN 98), Santa Fe, NM, June 14-21, 1998High Energy Physics - Phenomenologytext