A case of ovarian arrhenoblastoma in a 14-year-old girl is reported. The patient presented with primary amenorrhea, severe diffuse hirsutism, moderate clitorial enlargement and slight decrease in breast size. Hormonal examinations revealed high plasma testosterone and androstenedione levels, normal plasma prolactin, drhydroepiandrosterone-sulphate, 17-alpha-hydroxyprogesterone, urinary 17 beta oestradiol, oestrone, FSH and LH. Androgen concentrations decreased under dexamethasone suppression test. Following tumor ablation menses occurred spontaneously and normal hormone patterns were observed.