  We have computed 8, 10, and 12 Gyr isochrones and physically consistent
models of zero-age red horizontal branch stars for stellar masses between 0.55
and 1.3~\msun, all at [Fe/H] $=+0.15$. Comparison to the NGC 6791 BVI
photometry of Ka{\l}u\.zny & Udalski (1992) and Montgomery, Janes & Phelps
(1994) yields an age of $10.0\pm0.5$ Gyr at an apparent distance modulus $
13.49 < \dmv < 13.70$. The color offsets required to fit the isochrones,
combined with the spectroscopic results of Friel & Janes, imply that the
foreground reddening to NGC 6791 lies in the range $0.24 > \ebv >0.19$ with
$+0.27 <$ [Fe/H] $<+0.44$.
  The zero-age horizontal branch models suggest that the red horizontal branch
stars of NGC 6791 have masses $\lesssim 0.7\msun$. The masses are similar to
those found for M67 red clump stars by Tripicco, Dorman & Bell (1993) and for
globular cluster red horizontal branch stars, despite higher and lower masses
(respectively) in those cases. This suggests the presence of a mechanism that
tends to reduce stellar envelopes on the zero-age horizontal branch {\it to} a
given mass rather than {\it by} a given amount.
