  The strange form factors of the proton are basic to an understanding of
proton structure, and are presently the focus of many experiments. Before the
strangeness effects can be extracted from data, it is necessary to calculate
and remove effects due to isospin violation, which exist independently of the
strange quark but which contribute nevertheless to the experimentally measured
``strange'' form factors. A discussion of the isospin violating contributions
to vector form factors is given here in the context of heavy baryon chiral
perturbation theory.
