It has been demonstrated in recent years that ultrasound can be used to measure common carotid artery intimal thickness; an increase in intimal thickness is regarded as an early stage of atherosclerosis. This study was designed to establish whether or not intimal thickness can be modulated by therapy. Twenty-nine patients with familial hyperlipoproteinemias had follow-up ultrasound of the common carotid artery after twenty-nine months of comprehensive therapy. In 21 patients with familial hypercholesterolemia, intimal thickness decreased from 0.83 to 0.68 mm (P < 0.01), in 9 with familial combined hyperlipoproteinemia, the decrease was from 0.77 to 0.74 mm (a decrease was seen in only 50% of patients). With the group taken as a whole, the larger decrease was observed in patients treated with statins while the reduction was less marked in those administered fibrates. The authors found a decrease in common carotid artery intimal thickness following hypolipidemic therapy in patients with hyperlipoproteinemias. Their impression is that this was a manifestation of atherosclerosis regression.