Although many patients with restenosis after balloon coronary angioplasty have recurrence of angina, others remain asymptomatic. To assess the clinical implications of asymptomatic coronary restenosis, we analyzed clinical and angiographic characteristics of 277 consecutive patients with restenosis, 133 (48%) of whom were asymptomatic (group I) and 144 (52%) symptomatic (group II). Restenosis was documented 6 to 9 months after the index procedure, or earlier if angina recurred, and was defined as a greater than 50% lumen narrowing (visual estimation). Group I (asymptomatic group) included fewer female (9% vs. 18%, p less than 0.05) and hypertensive patients (38% vs. 56%, p less than 0.005) and more patients with a previous myocardial infarction (48% vs. 28%, p less than 0.05) and single-vessel disease (67% vs. 55%, p less than 0.05). Before angioplasty, symptoms had lasted for a shorter period (10 +/- 25 vs. 23 +/- 42 months, p less than 0.001), ischemia after a recent infarction was a more frequent indication (21% vs. 10%, p less than 0.05) and total revascularization more frequently obtained (74% vs. 63%, p less than 0.05) in group I than in group II patients. Only a normal blood pressure, previous myocardial infarction, single-vessel disease and a shorter duration of symptoms were independent correlates of asymptomatic restenosis. No differences were found in stenosis severity before angioplasty (90% in both groups) or after angioplasty (22% +/- 12% vs. 24% +/- 16%).(ABSTRACT TRUNCATED AT 250 WORDS)