  The two galactic `microquasars' with superluminal radio jets have been quite
active during 1996, generatinga variety of studies involving both NASA and
ground-based observatories. GRS~1915+105 has displayed dramatic accretion
instability in observations with RXTE, revealing X-ray light curves and
emission states unlike anything previously seen. Variable QPOs in the range of
0.07--10 Hz have been monitored with the capability to track the individual
oscillations. The QPO amplitude is as high as 40% of the mean flux, while both
amplitude and phase lag increase with photon energy. The results imply a direct
link between the QPO mechanism and the origin of the energetic electrons
believed to radiate the X-ray power-law component. GRS1915+105 also displays a
transient yet stationary QPO at 67 Hz. The other source, GRO J1655-40, is an
optically established black hole binary. Recent optical reports include an
excellent model for the binary inclination and masses, while an optical
precursor to the April 1996 X-ray outburst has been measured. We report new
results from recent RXTE observations. GROJ1655-40 has displayed both the
canonical ``soft/high'' and ``very high'' X-ray states, with QPOs at 8--22 Hz
during the latter state. In addition, there is a high-frequency QPO at 300 Hz.
The rapid oscillations in these sources are suspected of providing a measure of
the mass and rotation of the accreting black holes, although several competing
models may be applied when evaluating the results.
