Exposure to excess androgens in utero induces irreversible changes in gonadotrophin secretion and results in disrupted reproductive endocrine and ovarian function in adulthood, in a manner reminiscent of the common clinical endocrinopathy of polycystic ovary syndrome (PCOS). We have recently identified an abnormality in early follicle development in PCOS which we suggested might be an androgenic effect. We propose that altered ovarian function in androgenized ewes is due to prenatal androgens not only causing an abnormality of gonadotrophin secretion, but also exerting a direct effect on the early stages of folliculogenesis. Therefore, in this study, we explored the possible differences between small preantral follicles in the ovarian cortex of androgenized female lambs with those of normal lambs. At 8 months of age, small ovarian cortical biopsies (approximately 5 mm 3