The paper analyzes the decay of any zero modes that might exist for a massless Dirac operator Hα (1i) ∇+Q, where Q is 4×4 matrix valued and of order O (∫x∫-1) at infinity. The approach is based on inversion with respect to the unit sphere in R3 and establishing embedding theorems for Dirac-Sobolev spaces of spinors f which are such that f and Hf lie in (Lp (R3))4, 1≤p<∞. © 2008 American Institute of Physics.