Variations in the physico-chemical properties of ketoconazole have been studied, following polymorphic changes caused by fusion-cooling processes or by recrystallization in solvents commonly used in the pharmaceutical industry. Changes in physico-chemical properties were measured by differential scanning calorimetry (DSC), infra-red, X-rays and HPLC. Results revealed changes in the peak temperature of the different recrystallizations and changes in their X-ray diffraction patterns. Infrared spectra of the samples indicated no changes in the chemical structure of ketoconazole. HPLC results indicated a decrease in the solubility except in one case. No degradation products were detected.