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), infrared, X-rays and HPLC. Results revealed changes in the peak temperature of the different recrystallization 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. The validated methods were applied for quantitative determination of ketoconazole in commercial and simulated emulsion formulations. Quantitative first derivative UV spectrometric determinations were made using the zero – crossing method at 257 nm, with methanol as background solvent.