Optical inspection of polished Czochralski-grown Ge wafers typically reveals the presence of surface pits similar to the Crystal Originated Particles (COP's) observed in silicon but in a wider variety of sizes and shapes. Computer simulation of vacancy clustering during the Cz germanium crystal growth suggests that the surface pits originate from large voids formed by the diffusion-limited clustering of an excess of vacancies. (c) 2005 American Institute of Physics.