The relation between restenosis and progression of atherosclerosis in other coronary segments after angioplasty was studied in 98 consecutive patients with 110 coronary stenoses successfully treated with angioplasty. At early angiographic restudy (5 +/- 2 months after angioplasty) 37 patients (38%) had restenosis (defined as a stenosis greater than or equal to 50% of the luminal diameter or loss of greater than or equal to 50% of the gain achieved by angioplasty); progression of atherosclerosis was observed in 4 patients with and 7 without restenosis (13 versus 11%, p = NS). Ninety of the 98 patients underwent a late angiographic restudy a mean of 34 +/- 11 months after angioplasty. Late restenosis was found in one patient. Progression of coronary artery disease (defined as a greater than or equal to 20% decrease in the diameter of a vessel initially narrowed by greater than or equal to 50% or a greater than or equal to 30% decrease when the initial stenosis was less than 50%) was examined in relation to restenosis in 85 of the 90 patients. It occurred in 9 of 27 patients with and 22 of 58 patients without restenosis (33 versus 38%, p = NS). Restenosis developed more rapidly than did progression of disease. Diameter stenosis increased from 35 +/- 8 to 73 +/- 11% at the early restudy in lesions with restenosis; in lesions with disease progression it increased from 9 +/- 18 to 20 +/- 28% (p less than 0.001) at the early restudy to 53 +/- 21% (p less than 0.001) at the late restudy.(ABSTRACT TRUNCATED AT 250 WORDS)