  The excess of high-Q2 events recently observed in deep-inelastic
positron-proton scattering at HERA has refuelled speculations on physics beyond
the standard model, in particular on low-mass leptoquark-type particles. We
review the theoretical framework for leptoquark interactions, and their
production and decay at HERA. Bounds on leptoquark masses and couplings, and
implications on other experiments are also discussed.
