PHYSICS AT ELFE

I review some central physics opportunities at the 15...30 GeV continu ous beam electron accelerator ELFE, proposed to be built in conjunctio n with the DESY linear collider. Our present detailed knowledge of sin gle parton distributions in hadrons and nuclei needs to he supplemente d bg measurements of compact valence quark configurations, accessible through hard exclusive scattering, and of compact multiparton subsyste ms which contribute to semi-inclusive processes. Cumulative (x > 1, x( F) > 1) processes in nuclei measure short-range correlations between p artons belonging to different nucleons in the same nucleus. The same c onfigurations may give rise to subthreshold production of light hadron s and charm. The challenges of understanding high energy charmonium pr oduction indicate that charmonium will be a sensitive probe of color d ynamics at ELFE. At low energies, charmonium forms inside the target n ucleus, allowing a determination of c (c) over bar bound state interac tions in nuclear matter.