Gravitational lensing of the farthest known supernova SN 1997ff

We investigate the effects of gravitational lensing due to intervening gala xies on the recently discovered Type Ia supernova at z similar to 1.7, SN 1 997ff, in the Hubble Deep Field North. We find that it is possible to obtai n a wide range of magnifications by varying the mass and/or the velocity di spersion normalization of the lensing galaxies. In order to be able to use SN 1997ff to constrain the redshift-distance relation, very detailed modeli ng of the galaxies to control the systematic effects from lensing is necess ary. Thus, we argue that, based on our current limited knowledge of the len sing galaxies, it is difficult to use SN 1997ff to constrain the values of Omega (M) and Omega (Lambda), or even to place severe limits on gray dust o bscuration or luminosity evolution of Type Ia supernovae.