The clinical and pathologic findings of five cases of “mesonephroma” of the ovary are reported. A discussion of the histogenesis of these lesions is presented. Four of the five cases showed evidence of metastasis. Two of the four cases with metastases died 4 and 8 months after the diagnosis was made. Three patients are alive, well and show no evidence of recurrence at the present time after periods of 7, 9 and 12 years. Two of these patients had metastases at the time the diagnosis was first made.