Rubrene (5,6,11,12-tetraphenyltetracene) single crystals were grown by using the solution-slow-cooling technique with 1-propanol (PrOH) solvent. Thin hexagonal crystals with an orthorhombic system, typically 300 x 200 x 50 mu m(3) in size, were obtained. The crystals had flat terraces (similar to 7 mu m) separated by monomolecular steps. Organic field-effect transistors (OFETs) with the single crystals showed carrier mobilities as high as similar to 1.6 cm(2) V-1 s(-1). We also obtained thin parallelogram-shaped crystals, typically 300 x 200 x 20 mu m(3) in size. X-ray diffraction analysis solved that the crystals belong to triclinic system. The crystals showed lower carrier mobilities of similar to 0.1 cm(2) V-1 s(-1). This is the first report on the growth and characterization of two polymorphs of rubrene crystal. (c) 2009 Elsevier B.V. All rights reserved.