Glycine methyltransferase from rat liver is a tetrameric enzyme with 292 amino acid residues in each identical subunit and catalyzes the AdoMet-dependent methylation of glycine to form sarcosine. The enzyme was crystallized by the hanging drop vapor diffusion method, using polyethylene glycol 4000 as a precipitant. The crystal belongs to the orthorhombic space group P2(1)2(1)2, with unit cell dimensions of a = 86.4, b = 175.7, c = 45.5 Angstrom and with two subunits in the asymmetric unit. The crystals diffract beyond 2.4 Angstrom resolution, and a set of 2.4 Angstrom resolution data were measured. (C) 1994 Academic Press, Inc.