Polymorphic transformation in Fluconazole (I) drug has been studied employing differential scanning calorimetry (DSC), X-ray diffraction and FT-IR techniques. Fluconazole (I) exhibited the sharp melting point at 138.4degreesC. Considerable under cooling was, however, observed for the drug during cooling. No indication of freezing of molten Fluconazole (I) was evident in the DSC curve recorded up to a temperature of 25 degreesC in the cooling cycle. Reheating of the sample obtained after cooling, produced the DSC pattern much different compared to that obtained in the first heating and consisted of a sharp exothermic peak beginning at 81 degreesC preceding the twin endothermic peak with an onset temperature of 135.3 degreesC. In addition to these two peaks, a small endothermic peak was also observed around 31 degreesC, which could be attributed to a glass transition with an associated relaxation. The precise glass transition temperature derived from the data collected from six different independent experiments was found to be (31.67 +/- 0.13) degreesC. X-ray diffraction pattern of the Fluconazole (I) indicated that the as received sample was crystalline. The molten Fluconazole on cooling, however, produced a glassy amorphous mass. The amorphous product on heating to temperature >81 'C transformed to Fluconazole (II) which subsequently changed to Fluconazole (I) prior to melting. The split endothermic peak beginning at 135.3degreesC recorded for the solidified Fluconazole sample is consistent with the observations made by X-ray diffraction. The observations made by employing DSC and X-ray diffraction were corroborated by FTr-IR data on the samples isolated at different stages in the experiments.