OBJECTIVE: To evaluate the influence of two ultra-low doses of oral continuous combined hormone therapy and placebo on metabolic parameters, and to assess safety endpoints and overall tolerability in healthy postmenopausal women. DESIGN: In a subpopulation of the Clinical study on Hormone dose Optimisation In Climacteric symptoms Evaluation (CHOICE) trial, lipids and parameters of glucose metabolism and hemostasis were analyzed in Nordic women (n = 158) at baseline and after 12 and 24 weeks of treatment with 0.5 mg 17beta-estradiol (E2) + 0.25 mg norethisterone acetate (NETA), 0.5 mg E2 + 0.1 mg NETA or placebo. Adverse events occurring from the first trial-related activity, whether related or not related to the study medication, were recorded for the entire population (n = 575) of the trial. The seriousness, relationship to treatment and the reason for withdrawal were reported. RESULTS: Both ultra-low-dose combinations were neutral to changes in lipid and lipoprotein, hemostasis parameters and carbohydrate metabolism during the trial. The incidence of serious adverse events was only 1% in respective treatment groups. Adverse events were the reason for withdrawal in only 2% and 6% of women in the 0.5 mg E2 + 0.25 mg and 0.1 mg NETA groups, and in 8% in the placebo group. No weight gain or change in blood pressure was reported during the trial in any of the study groups. CONCLUSION: The treatments had neutral effects on metabolic parameters in the study population. Excellent tolerability of both ultra-low doses resulted in high completion rates.