To evaluate the rate and predictive factors of restenosis after multivessel percutaneous transluminal coronary angioplasty (PTCA), 122 consecutive patients with multivessel PTCA performed in the same setting were included in a prospective study. Systematic angiographic control at 6 months was performed in 112 patients (92%). Restenosis (increase > 20% and stenosis > 50%) was found in 62 patients (55%) and 82 of 254 segments (32%) were dilated. Statistical analysis identified the number of successfully dilated segments as the only predictor of restenosis by patient (2.4 +/- 0.7 vs 2.0 +/- 0.7; p < 0.03), and the greater degree of residual stenosis as the only predictor of restenosis by lesion (30 +/- 14% vs 23 +/- 12%; p < 0.005). Twenty-two of 62 restenosed patients (35%) were asymptomatic (group 1). Baseline clinical and angiographic characteristics of these patients were similar to those with symptomatic restenosis (n = 40; group 2) and without restenosis (n = 50; group 3). Repeat revascularization for restenosis was used only in symptomatic patients (re-PTCA in 36; bypass surgery in 4). After a mean follow-up of 75 +/- 24 months, clinical status, and rates of cardiac death and myocardial infarction were similar in the 3 groups. Medical care was similar in groups 1 and 3, and higher in group 2. However, the rate of repeat revascularization for progression of disease was similar in the 3 groups (29%). In conclusion, restenosis is a frequent event after multivessel PTCA and is strongly related to the number of successfully dilated segments.(ABSTRACT TRUNCATED AT 250 WORDS)