  Physics from the polarized electron or positron beam colliding with the
unpolarized proton beam at HERA-II as well as from the unpolarized ep
collisions at HERA-I is discussed. Results shown include (i) inclusive neutral
and charged current cross sections and structure functions measurements at
HERA-I, (ii) the impact of these measurements on parton density functions, on
electroweak parameters and searches for new physics and (iii) the first results
at HERA-II and its future prospects.
