  We describe a program that we have embarked on to estimate the spins of
stellar-mass black holes in X-ray binaries. We fit the continuum X-ray spectrum
of the radiation from the accretion disk using the standard thin disk model,
and extract the dimensionless spin parameter a* = a/M of the black hole as a
parameter of the fit. We have obtained results on three systems, 4U 1543-47 (a*
= 0.7-0.85), GRO J1655-40 (0.65-0.8), and GRS 1915+105 (0.98-1), and have
nearly completed analysis of two additional systems. We anticipate expanding
the sample of spin estimates to about a dozen over the next several years.
