Human placental annexin IV, a member of the annexin family of calcium and phospholipid-binding proteins, has been crystallized by the vapour diffusion method in the presence of calcium, using polyethylene glycol 8000. The crystals are orthorhombic, space C222(1), cell dimensions a = 105.4 A, b = 115.7 A, c = 80.7 A and diffract to at least 2.5 A resolution on a synchrotron source.