The grain boundary groove shapes for solid aminomethylpropanediol in equilibrium with eutectic aminomethylpropanediol-neopentylglycol liquid were directly observed by using a horizontal temperature gradient stage. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficient, solid-liquid interfacial energy and grain boundary energy of solid aminomethylpropanediol in equilibrium with eutectic aminomethylpropanediol-neopentylglycol liquid have been determined to be (5.3 +/- 0.5) x 10 (8) K m, (8.5 +/- 1.3) x 10 (3) J m (2) and (16.8 +/- 2.9) x 10 (3) J m (2), respectively. (C) 2008 Elsevier B.V. All rights reserved.