The crystal preparation and preliminary neutron diffraction analysis of gamma-chymotrypsin are presented. Large hydrogenated crystals of gamma-chymotrypsin were exchanged into deuterated buffer via vapor diffusion in a capillary and neutron Laue diffraction data were collected from the resulting crystal to 2.0 A resolution on the LADI-III diffractometer at the Institut Laue-Langevin (ILL) at room temperature. The neutron structure of a well studied protein such as gamma-chymotrypsin, which is also amenable to ultrahigh-resolution X-ray crystallography, represents the first step in developing a model system for the study of H atoms in protein crystals.