Growth kinetics and diffraction properties of monoclinic crystals of eubacterial Thermus thermophilus aspartyl-tRNA synthetase-1 (AspRS-1) prepared in the presence of polyethylene glycol and agarose are studied. Their solubility and two-dimensional phase diagram are compared with those of orthorhombic crystals which grow in the presence of sodium formate or ammonium sulfate. The growth mechanism of the novel crystals was monitored by atomic force microscopy. The gel stabilizes the crystal lattice under the cryogenic conditions used for structure determination at high resolution.