Neurofibromin (MW 320 kDa) is the protein responsible for the pathogenesis of neurofibromatosis type 1 (NF1), one of the most common genetic diseases worldwide. The neurofibromin GAP-related domain (GRD, MW 38 kDa) possess a Ras-specific GTPase-activating protein property, which is at present its only clear biochemical function. This article describes the study of the bacterial production and preliminary X-ray crystallographic analysis of a neurofibromin fragment located at the C-terminal end of the GRD, which contains a region reported to be homologous to the yeast Sec14p lipid exchange protein. Of the three crystal variants obtained, a tetragonal form diffracted to a resolution of at least 2.3 A.