The monocrystal of MBBA was grown from the polycryst. sample in a thin capillary at -163 Deg by a new method using miniature zone melting procedure with a focused IR laser beam for producing a local molten zone. The crystals are monoclinic, space group P21, with a 14.908(4), b 8.391(3), c 18.411(4) .ANG., and b 96.40(2) Deg; Z = 2 (3 mol./Z); R = 0.058 for 2256 reflections. At. coordinates are given. The 3 independent mols. in the crystal have slightly different conformations but the geometric parameters are normal. The mol. packing is smectic-like and is characterized by the presence of layers parallel to (001), the thickness of the layer is close to the c axis of the unit cell. The relationship between the different phases of solid MBBA is discussed.