Malignant oncocytoma(oxyphil cell adenoma) is a extremely rare malignant tumor of the salivary glands and almost occurs in the parotid gland. A case of malignant oncocytoma of the parotid gland occurring in a 63 year old man is reported. Establishing a diagnosis of malignant oncocytoma essentially requires the application of two sets of criteria to the tumor under examination. First, the tumor cells must be identified as oncocyte and second, malignancy must be determined. Histochemical stains are not as useful as generally believed. Electron microscopy confirms the diagnosis by demonstrating an abundance of mitochondria. The diagnosis of malignant oncocytoma depends on several additional criteria in addition to cellular and nuclear pleomorphism, including lack of encapsulation, local infiltration, perineural and intravascular growth, and regional and/or distant metastasis. Satisfactory results from surgical resection and postoperative radiotherapy in our patient serve as additional experience in the treatment of this rare malignancy.