  We have obtained high resolution images of the central regions of 14
reverberation-mapped active galactic nuclei (AGN) using the Hubble Space
Telescope Advanced Camera for Surveys High Resolution Camera to account for
host-galaxy starlight contamination of measured AGN luminosities. We measure
the host-galaxy starlight contribution to the continuum luminosity at 5100 A
through the typical ground-based slit position and geometry used in the
reverberation-mapping campaigns. We find that removing the starlight
contribution results in a significant correction to the luminosity of each AGN,
both for lower luminosity sources, as expected, but also for the higher
luminosity sources such as the PG quasars. After accounting for the host galaxy
starlight, we revisit the well-known broad-line region radius--luminosity
relationship for nearby AGN. We find the power-law slope of the relationship
for the H beta line to be 0.518 +/- 0.039, shallower than previously reported
and consistent with the slope of 0.5 expected from the naive theoretical
assumption that all AGN have, on average, the same ionizing spectrum and the
same ionization parameter and gas density in the H beta line-emitting region.
