The acceptability and skin reaction of Estraderm Transdermal Therapeutic Systems as a function of climatic variability were examined in various zones which alter considerably in their temperature and humidity. An open, noncomparative prospective study was carried out in four institutional out-patient menopausal clinics in varying climatic areas. Eighty symptomatic postmenopausal patients without previous estrogen replacement were examined. Estraderm T.T.S. 50 was applied twice weekly in four weekly cycles. Norethisterone-acetate tablets (1 mg), were taken orally for 12 consecutive days. Using a questionnaire, the subjects were asked about the efficacy of the treatment on postmenopausal symptoms, the adhesiveness and tolerability. The results were matched with the meteorological conditions. The duration of the study was 6 months. Acceptability of Estraderm T.T.S. is high (78.7%). Discontinuation of treatment was found in 21.3% of the study group. The main reason for discontinuation is due to skin reactions which occurred in 14 of the 80 patients (17.5%). Meteorological conditions in this study did not influence the rate of skin reactions. No difference in acceptability of the treatment was found in relation to the mean temperature and mean humidity as registered in the dry desert and the humid coastal areas.