To determine whether significant angiographic narrowing and restenosis after successful coronary balloon angioplasty is a specific disease entity occurring in a subset of dilated lesions or whether it is the tail end of a gaussian distributed phenomenon, 1,445 successfully dilated lesions were studied before and after coronary angioplasty and at 6-month follow-up study. The original cohort consisted of 1,353 patients of whom 1,232 underwent repeat angiography with quantitative analysis (follow-up rate 91.2%). Quantitative angiography was carried out off-line in a central core laboratory with an automated edge detection technique. Analyses were performed by analysts not involved with patient care. Distributions of minimal lumen diameter before angioplasty (1.03 +/- 0.37 mm), after angioplasty (1.78 +/- 0.36 mm) and at 6-month follow-up study (1.50 +/- 0.57 mm) as well as the percent diameter stenosis at 6-month follow-up study (44 +/- 19%) were assessed. The change in minimal lumen diameter from the post-angioplasty angiogram to the follow-up angiogram was also determined (-0.28 +/- 0.52 mm). Seventy lesions progressed toward total occlusion at follow-up. All observed distributions approximately followed a normal or gaussian distribution. Therefore, restenosis can be viewed as the tail end of an approximately gaussian distributed phenomenon, with some lesions crossing a more or less arbitrary cutoff point, rather than as a separate disease entity occurring in some lesions but not in others.