The latest Black Hole X-ray Transient, XTE J1118+480, is very bright (V=13), and lies at high galactic lattitude near to the ``Lockman Hole'', hence suffers very little interstellar absorption and reddening (Garcia et al IAU Circ 7392). This makes it extremely suitable for multiwavelength studies. Satellite observations of this source are scheduled: EUVE observations: April 8 from 02:20UT until 17:07UT HST observations: April 8 from 12:06UT until 19:35UT RXTE observations: April 8 from 13:08UT until 13:56UT and infrared coverage from UKIRT (Mauna Kea, Hawaii) is scheduled April 8 from 12:00UT until 13:30UT Optical photometric modulations have been discovered with a 4.1 hour period, see Lew Cook's data at http://vsnet.geocities.com/lcoo/xte1118.htm The Coordinates of the source are (Masi, IAU Circ 7392): R.A. = 11h18m10s.85 Decl. = +48o02'12".9 (equinox 2000.0) and a finding chart is given on http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Xray/xtej1118.html High time resolution (faster than 10s cycle time) light curves simultaneous with HST or RXTE, calibrated UBVRI photometry, and optical spectrophotometry would be particularly useful. Anyone obtaining data will be invited to participate in our multiwavelength collaboration studying this source. The USA satellite will observe for frequent 15-20 minute segments between April 10 and April 16, and will continue to monitor the source for as long as it remains active. Further satellite observations are tentatively scheduled for April 17 or 18, April 27, 28 or 29 (HST), April 13 (RXTE). We will post the exact timings when these are known. Carole Haswell, c.a.haswell@open.ac.uk Rob Hynes, rih@astro.soton.ac.uk Wei Cui, cui@space.mit.edu Sylvain Chaty, s.chaty@open.ac.uk Christopher Mauche, mauche@cygnus.llnl.gov Chris Shrader, shrader@grossc.gsfc.nasa.gov Reba M. Bandyopadhyay, reba@xeus.nrl.navy.mil