We studied the progression of coronary angiographic findings in a series of 10 patients with homozygous familial hypercholesterolaemia. All patients had medical treatment; six had additional surgical treatment. They were followed over a period of 2-10 years (mean follow-up five years). Three types of evolution were observed: (a) normal coronary angiography with no development of any lesion over a period of eight years in two young patients; (b) regression of proximal coronary stenoses in three patients, and (c) progression of coronary angiographic status in five patients. A different evolution of proximal and distal segment lesions was observed; while more than two-thirds of proximal segments stenoses improved and no proximal lesion increased with a 45% decrease in plasma cholesterol level, no improvement was obtained at the distal level. Distal lesions tended to increase and new lesions appeared in spite of a major plasma cholesterol level reduction. When early treatment results in a cholesterol plasma level decrease of more than 45% and a level of about 4 g l-1 over a very long period of time, the coronary prognosis may be good.