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 .

Subject headings : accretion , accretion disks – black hole physics