Luteoma in pregnancy is a rare tumour (about 100 published cases) and it is rarely associated with signs of virilisation (28 published cases). A visiting luteoma in pregnancy in primigravid woman of 27 years of age is reported and compared with other cases in the literature. A study of the androgen secretions before and after pregnancy and especially the levels of androgens in the peripheral blood, the ovarian vein and in the tumour ware carried out so that metabolic pathways of the production of the androgens could be worked out. The particular circumstances of the unexpected appearance of this luteoma during an H.C.G. stimulation test (Human Chorionic Gonadotrophin) gives an opportunity to define the role of this hormone in its occurrence. Finally, a review of the literature makes it possible to draw up a history of the usual behaviour of these virilising luteomas in pregnancy: they usually show up in the second trimester of pregnancy, and the overriding role is played by testosterone with virilisation of female fetuses.