A non-haemorrhagic fibrin(ogen)olytic metalloproteinase from the venom of Agkistrodon acutus has been crystallized by the hanging-drop method. The crystals belong to space group P3(1)21, with unit-cell parameters a = b = 80.57, c = 66.77 A and one molecule in the asymmetric unit. X-ray diffraction data were collected to 1.86 A resolution.