  We calculate spectral models of advection-dominated accretion flows, taking
into account the possibility that significant mass may be lost to a wind. We
apply the models to the soft X-ray transient V404 Cyg in quiescence and the
Galactic center source Sgr A*. We show that there are qualitative degeneracies
between the mass loss rate in the wind and parameters characterizing the
microphysics of the accretion flow; of particular importance is $\delta$, the
fraction of the turbulent energy which heats the electrons. For small $\delta$,
current observations of soft X-ray transients and Sgr A* suggest that at least
$\sim 10 %$ of the mass originating at large radii must reach the central
object. For large $\delta \sim 0.3$, however, models with significantly more
mass loss are in agreement with the observations. We also discuss constraints
on advection-dominated accretion flow models imposed by recent radio
observations of NGC 4649 and other nearby elliptical galaxies. We conclude by
highlighting future observations which may clarify the importance of mass loss
in sub-Eddington accretion flows.
