The orientation dependence of pit propagation in single-crystal beryllium (Be) is compared to observations for single-crystal zinc (Zn). Pits formed on the prism planes of both Be and Zn were characterized by interiors which had crystallographically oriented, parallel plates of unattacked material. In Be, the orientation of the unattacked material had a 90degrees asymmetry with respect to those formed in Zn. To explain this difference, the electron density distribution for low index planes in Be and Zn was analyzed. A conceptual model for crystallographic pit propagation that considers the role of orientation dependent metal-metal bonding is introduced. (C)' 2003 The Electrochemical Society.