In this work, we report the crystallization of cholesterol in ethanol solution and in three different hydro;,Yel media: Letramethyl orthosilane, sodium metasilicate, and poly(vinyl)alcohol, whose structures are similar to the gel like polymer structure of mucin, which is found in the mucus present in bile stone formation. The monohydrated triclinic phase was identified in all the samples by means of X-ray powder diffraction. The characteristic polymorphic crystalline transition of the anhydrous cholesterol was detected by differential thermal analysis and modulated differential scanning calorimetry only in crystals grown in ethanol, sodium silicate, and tetramethyl orthosilane. Finally, hysteresis of the phase transition temperature was measured by modulated differential scanning calorimetry in crystals grown in ethanol. The biological implications of the crystallization of cholesterol for bile stones formation are discussed in the last part of this contribution. (C) 2013 Elsevier EN. All rights reserved.