Virilization is usually associated with amenorrhea, infertility and ovarian stromal lesions. Paradoxically, however, it may also be seen in pregnancy; this type of virilization is rare and accompanies ovarian thecosis. Thecosis, also known as thecomatosis and stromal thecosis, is a complex assortment of types of ovarian stromal proliferation associated with various types and amounts of hormonal activity. A patient had progressive virilization that began about seven years after menarche. Nonetheless, she had six pregnancies and bore five normal living children. Her last child, a female, was not affected by the high maternal testosterone levels. The patient's virilization was associated with an ovarian stromal hyperplasia classified as combined thecosis. In this case, as in some others, there was reason to suspect a genetic basis for such progressive virilization with retained fertility; an analysis of it provides insight into the complex nature of ovarian stromal hyperplasia and hormonal activity.