In this study we compared the effects of either Aminoglutethimide (AGL) or Tamoxifen (TAM) therapy on the genital tract of postmenopausal women with advanced breast cancer. Thus, 15 patients treated with AGL, and 10 patients treated with TAM underwent gynaecological examination, during which vaginal smears were taken. All smears were reviewed in blind by one pathologist for determination of karyopycnotic indices (KI). Under TAM, no significant clinical abnormality was observed, except in one patient who had a small (histologically benign) endocervical polyp, easily removed during the examination. As reported by others, smears made under TAM therapy were generally characterized by high KI, indicating that an hormonal, estrogen-like stimulation remained present in these patients. On the contrary, most women under AGL had some evidence of vulvovaginal atrophy, which was unvariably associated with low KI on smears. Among the latter, four had severe dystrophic lesions consisting of leukoplasia (1), kraurosis (2) or lichen sclerous and atrophicus (1). It is therefore recommended not to neglect the systematic practice of gynaecological examination in patients with advanced breast cancer under endocrine therapy. These observations also indicate that AGL and TAM exert entirely opposite effects on the vaginal mucosa, which is a very sensitive estrogen-target tissue. In good agreement with former endocrine studies, AGL acts as a potent suppressor of estrogens resulting in severe mucosal atrophy. On the contrary, TAM seems nearly always to display some agonistic hormonal stimulation.