Two novel single crystals Of L-tartaric acid-nicotinamide (LTN, 2HOOC HC(OH)HC(OH)COO-.2C(5)H(4)NH(+) CONH2.H2O,) and D-tartaric acid Nicotinamide (DTN, 2HOOCHC(OH)HC(OH)COO-.2C(5)H(4)NH(+)CONH(2).H2O), good quality organic nonlinear optical (NLO) materials have been successfully grown by the temperature lowering method from aqueous solution. Solubility curves of both LTN and DTN have been determined in water. The solubility of both LTN and DTN steadily moved upward along with the uninterrupted rise of the solution temperature. Effects of different solvents on growth of LTN and DTN single crystals were compared. The LTN single crystal in size 12 x 42 x 2 mm(3) was grown in the deionized water for 5 days while DTN single crystal in size 28 x 12 x 3 mm(3) was grown for only 12 h. The transmission ranges of both LTN and DTN single crystals have been found to be between 280 and 1900nm. (C) 2003 Elsevier B.V. All rights reserved.