  A massless up quark is an intriguing solution to the strong CP problem. We
discuss how lattice computations can be used in conjunction with chiral
perturbation theory to address the consistency of $m_u=0$ with the observed
hadron spectrum and interactions. It is not necessary to simulate very light
quarks-three flavor partially quenched computations with comparable sea and
valence quark masses on the order of the strange quark mass could suffice.
