Glutamate is the major excitatory neurotransmitter and its metabotropic glutamate receptor (mGluR) plays an important role in the central nervous system. The ligand-binding domain (LBD) of mGluR subtype 7 (mGluR7) was produced using the baculovirus expression system and purified from the culture medium. The purified protein was characterized by gel-filtration chromatography, SDS-PAGE and a ligand-binding assay. Crystals of mGluR7 LBD were grown at 293 K by the hanging-drop vapour-diffusion method. The crystals diffracted X-rays to 3.30 A resolution using synchrotron radiation and belong to the trigonal space group P3(1)21, with unit-cell parameters a = b = 92.4, c = 114.3 A. Assuming the presence of one protomer per crystallographic asymmetric unit, the Matthews coefficient V(M) was calculated to be 2.5 A3 Da(-1) and the solvent content was 51%.