  With a redshift of z~1.7, SN 1997ff is the most distant type Ia supernova
discovered so far. This SN is close to several bright, z=0.6-0.9 galaxies, and
we consider the effects of lensing by those objects on the magnitude of SN
1997ff. We estimate their velocity dispersions using the Tully-Fisher and
Faber-Jackson relations corrected for evolution effects,and calculate, applying
the multiple-plane lensing formalism, that SN 1997ff is magnified by 0.34+-0.12
mag. Due to the spatial configuration of the foreground galaxies, the shear
from individual lenses partially cancels out,and the total distortion induced
on the host galaxy is considerable smaller than that produced by a single lens
having the same magnification. After correction for lensing, the revised
distance to SN 1997ff is m-M=45.5 mag, which improves the agreement with the
Omega_M=0.35, Omega_Lambda = 0.65 cosmology expected from lower-redshift SNe
Ia, and is inconsistent at the ~3 sigma confidence level with a uniform gray
dust model or a simple evolution model.
