  The Vafa-Witten equations on an oriented Riemannian 4- manifold are first
order, non-linear equations for a pair of connection on a principle SO(3)
bundle over the 4-manifold and a self-dual 2-form with values in the associated
Lie algebra bundle. The main theorem in this paper characterizes in part the
behavior of sequences of solutions to the Vafa-Witten equations which have no
convergent subsequence. The paper proves that a renormalization of a
subsequence of the self-dual 2-form components converges on the complement of a
closed set with Hausdorff dimension at most 2, with the limit being a harmonic
2-form with values in a real line bundle.
