The true struma ovanii is a rare teratomatoustissue neoplasia, composed with typical thyroid tissue. Generally it is asymptomatic or only deterand mines a mild hypogastric weighting feeling. In a few subjects this neoplasm is secreting and rise to hyperthyroidism. The Authors describe the clinical and anatomopathological characteristics of 3 cases of true struma ovarii come to their observation. No malignant histologic features in any of them was seen. In the relatively short period of post surgical observations no women showed relapses or metastases. This confirms that true struma ovaeiiis usually a benign tumor.