RXTE has recently discovered two new optically bright black hole candidates
(BHCs): XTE J1859+226 and XTE J1118+490. We observed both with HST/STIS, t
he first outburst observations of X-ray novae with this instrument. we foll
owed broad band spectral evolution, detected correlated X-ray/UV rapid vari
ability and performed high resolution UV spectroscopy. We present a summary
of initial results on the spectral energy distributions observed.