The ovary is an active source of androgen secretion. This is regulated largely by LH but by insulin and other factors as well. Functional states include PCO as well as stromal hyperthecosis, which often mimics a neoplasm. Ovarian neoplasms are often gonadotropin responsive. Both functional and nonfunctional tumors may give rise to elevated androgen levels. Clinical history and the accurate assessment of testosterone measurements aid in the correct diagnosis of an androgen-secreting tumor. Imaging techniques, particularly vaginal ultrasound, are extremely valuable in making the diagnosis. Selective venous catheterization, although useful, should not be the primary diagnostic technique.