  We present model X-ray spectra of accreting black holes with
advection-dominated accretion flows, paying attention to thermal emission lines
from the hot plasma. We show that the Advanced X-ray Astrophysical Facility
(AXAF) might be able to observe lines from X-ray binaries such as V404 Cyg in
quiescence, the Galactic Center black hole Sagittarius A*, and the nuclei of
nearby galaxies such as M87. Line intensities can provide new diagnostics to
study the accreting plasma in these and related systems.

Astrophysics