Objective: Mucormycosis is an aggressive and fatal invasive fungal infection. It is usually documented in patients with uncontrolled diabetes. Mucor is often recognized as a triad of symptoms, such as uncontrolled diabetes mellitus, periorbital infection and meningoenchephalitis. We report a case o2120f rhinocerebral mucormycosis in a patient with hyperglycemic hyperosmolar syndrome. Case A 66 years old man presented to hospital with general weakness and febrile sensation. He had a past medical history of type 2 diabetes mellitus, hypertension, and bladder cancer which had been surgically removed 4 years ago. On examination the patient was found to have swelling, redness, and swelling of left periorbital area. Laboratory results on admission showed an elevated white cell count 22.1 × 103/㎣ and C-recative protein 25.53 mg/dL; blood glucose 1050 mg/dL; creatinine 2.26 mg/dL, all of which were consistent with infection, hyperglycemic hyperosmolar state, and renal failure. A non-contrast computed tomography scan of the head was performed revealing multifocal infiltrative soft tissue swelling in left periorbital, perinasal, and retormaxillary fat area and mucosal thickening in both maxillary and ethmoid sinuses. The patient was commenced on hydration, insulin therapy, and antimicrobial therapy. After a total of 4 days of treatment, treatment was discontinued due to discharge against medical advice. After 1 day from discharge, the patient was hospitalized again at intensive care unit due to semi-coma mental status. The patient was intubated. Laboratory results were similar to those on the previous admission. After an antimicrobial therapy, nasal cavity can be examined by nasopharyngoscope. The black-colored crusts were seen in the nasal cavity and punch biopsy was done. The patient was commenced on amphotericin B therapy. The biopsy showed mucormycosis. Despite treatment the patient expired. Conclusion: Mucormycosis is a life threatening fungal infection predominately seen in diabetic patietns.