The NADP-linked glutamate dehydrogenase from Neurospora crassa has been crystallized by the hanging-drop method of vapour diffusion in the presence of 0.1 M glutamate. The crystals are trigonal and are in space group P3(1)21 with unit-cell dimensions of a = b = 196.6, c = 102.0 A and with a trimer in the asymmetric unit. A full structure determination of this enzyme will lead to an understanding of the molecular basis of inter-allelic complementation observed with hybrid hexamers of naturally occurring mutants.