  Measurement of the neutral weak vector form factors of the nucleon provides
unique access to the strange quark content of the nucleon. These form factors
can be studied using parity-violating electron scattering. A comprehensive
program of experiments has been performed at three accelerator laboratories to
determine the role of strange quarks in the electromagnetic form factors of the
nucleon. This article reviews the remarkable technical progress associated with
this program, describes the various methods used in the different experiments,
and summarizes the physics results along with recent theoretical calculations.
