To investigate the effect of discontinuation of hormone replacement therapy on the intima thickness and blood flow velocity of the common carotid artery. The thickness of the left common carotid artery intima and maximal systolic blood velocity were measured by real-time and Doppler ultrasonography in 75 healthy postmenopausal women starting sequential combined hormone replacement therapy. The measurements were performed at the start and after 6 and 12 months of the therapy. Thirty two women decided to discontinue the therapy after 6 months, whereas 43 continued. In the group that continued with the hormone replacement therapy, a significant decrease was recorded in the mean baseline values for carotid artery intima thickness and flow velocity at 6 months (0.35+0.11 vs 0.54+0.19 mm and 0.73+0.16 vs 0.87+0.19 m/s, respectively, p?0.001) and 12 months of follow-up (0.36+0.1 mm and 0.72+0.15 m/s vs baseline, respectively, p?0.001). In women who discontinued the therapy, there were significant deviations from the baseline values in the intima thickness (0.36+0.11 vs. 0.59+0.09 mm, p=0.010) and flow velocity (0.75+0.14 vs. 0.85+0.16 m/s, p?0.001) at 6 but not at 12 months of the follow-up (0.55+0.12 mm, and 0.85+0.17 m/s vs baseline; p=0.148 and p=0.965, respectively). Decreased flow velocity and reduced intima thickness were directly related to blood vessel wall dilatation after estrogen component of hormone replacement therapy. Discontinuation of the hormone replacement therapy returned the flow velocity and intima thickness to their baseline values.