A single centre randomised placebo-controlled trial was performed to assess the 2-year effects of hormone replacement therapy compared to placebo on mechanical arterial properties in 99 perimenopausal women recruited from the general population. The trial was double-blind with respect to a sequential combined regimen of oral 17beta-oestradiol and desogestrel (17betaE(2)-D) and the placebo group and open with respect to combination of conjugated equine oestrogens and norgestrel (CEE-N). At baseline, distensibility and compliance of the common carotid artery were measured non-invasively with B-mode ultrasound and a vessel wall movement detector system, and the distensibility coefficient (DC) and compliance coefficient (CC) were calculated. Measurements were repeated after 6 and 24 months. Change in DC and CC in treatment groups was compared to placebo. After 24 months, changes for 17betaE(2)-D compared to placebo were -1.4x10(-3)/kPa (95% CI -4.4; 1.7, P=0.39) for DC and 0. 26 mm(2)/kPa (95% CI -0.01; 0.53, P=0.07) for CC. Changes for CEE-N compared to placebo were 0.4x10(-3)/kPa (95% CI -1.0; 1.9, P=0.79) and 0.11 mm(2)/kPa (95% CI -0.14; 0.37, P=0.40). For systolic blood pressure (SBP), diastolic blood pressure (DBP) and arterial lumen diameter no changes were found. In this study no significant differences in changes in distensibility and compliance were found between perimenopausal women using 17betaE(2)-D or CEE-N and women using placebo after 6 and 24 months.