Thirty postmenopausal women with vaginal atrophy were treated with a vaginal cream or vaginal suppositories containing 0.5 mg estriol (OvestinR, Organon, The Netherlands). The preparations were given daily for 14 days and then during the next 6 weeks a maintenance dose was applied twice a week. Cervical mucus, vaginal cytology and the endometrium were studied. Blood samples were analysed for unconjugated and conjugated estriol, FSH, LH, prolactin and sex hormone binding globulin capacity, before and after 2 weeks of treatment. Subjective relief of vaginal symptoms was reported by all patients. Restoration of vaginal mucosa was confirmed by colposcopy. Some women noted a feeling of transient "vaginal heat" during the first days of treatment; otherwise no side effects were reported. Higher values for Spinnbarkeit, ferning and karyopyknotic index were found for the cream group on day 14. No endometrial stimulation was detected as judged by light microscopy in any of the samples. No significant differences between the preparations were found for any of the hormone variables, or sex hormone binding globulin capacity, except for prolactin levels after 2 weeks of treatment. Possible reasons for the disparity between the two preparations regarding peripheral variables are discussed.