Bunyamwera virus (BUNV) is the prototypic member of the Bunyaviridae family of segmented negative-sense RNA viruses. The BUNV nucleocapsid protein has been cloned and expressed in Escherichia coli. The purified protein has been crystallized and a complete data set has been collected to 3.3 Å resolution at a synchrotron source. Crystals of the nucleocapsid protein belong to space group C2, with unit-cell parameters a = 384.7, b = 89.8, c = 89.2 Å, β = 94.4°. Self-rotation function analysis of the X-ray diffraction data has provided insight into the oligomeric state of the protein as well as the orientation of the oligomers in the asymmetric unit. The structure determination of the protein is ongoing. © 2006 International Union of Crystallography. All rights reserved.