  Gravitationally-lensed quasars can be discovered as a by-product of galaxy
redshift surveys. Lenses discovered spectroscopically in this way should
require less observational effort per event than those found in dedicated lens
surveys. Further, the lens galaxies should be relatively nearby, facilitating a
number of detailed observations that are impossible for the more common
high-redshift lenses. This is epitomised by the wide range of results that have
been obtained from Q 2237+0305, which was discovered as part of the Center for
Astrophysics redshift survey, and remains the only quasar lens discovered in
this way. The likelihood of this survey yielding a lens is calculated to be
about 0.03, which is an order of magnitude larger than previous estimates due
to two effects. Firstly, the quasar images themselves increase the observed
flux of the lens, so that lens galaxies up to a magnitude fainter than the
nominal survey limit must be included in the calculation. Secondly, it is
possible for lensed quasars with extremely faint deflectors to enter the survey
due to the extended morphology of the multiple images. Extrapolating these
results to future surveys, the 2 degree Field galaxy redshift survey should
contain between 10 and 50 lenses and the Sloan Digital Sky Survey should yield
between 50 and 300 lenses, depending on the cosmological model and the
observing conditions.
