  The gamma-ray observatory INTEGRAL, launched in October 2002, produces a
wealth of discoveries and new results on compact high energy Galactic objects,
nuclear gamma-ray line emission, diffuse line and continuum emission, cosmic
background radiation, AGN and high energy transients. Two important
serendipitous discoveries made by the INTEGRAL mission are new classes of X-ray
binaries, namely the highly-obscured high-mass X-ray binaries, and the
super-giant fast transients. In this paper I will review the current status of
these discoveries.
