Monocyte chemoattractant protein-1 (MCP-1) plays a fundamental role in monocyte recruitment and has been implicated in atherosclerosis. The present study tested the hypothesis that increased levels of MCP-1 are associated with an increased risk for restenosis post stent implantation. The plasma MCP-1 antigen levels were measured pre-stenting, and at 24 and 48 h and 6 months post stenting in 41 patients with stable exertional angina (SEA) who had undergone successful stent implantation. Nineteen patients with chest pain syndrome were selected as a control group. Initial plasma MCP-1 antigen levels (mean +/- SE, pg/ml) in the patients with SEA were significantly higher than those in the control group (852.3+/-51.4 vs 418.2+/-26.7, p<0.001). The patients with SEA were divided into 2 groups based on follow-up angiographic findings: 17 patients with restenosis (R group); 24 patients without restenosis (N group). The lesion was significantly longer in the R group than in the N group (p<0.03). Plasma MCP-1 antigen levels at pre-stenting were not significantly different between the 2 groups (820.6+/-69.1 in the R group vs 874.7+/-73.8 in the N group). Serial changes of plasma MCP-1 levels were plotted as percent changes from the initial levels (mean +/- SE, %) and were significantly higher in the R group than in the N group at 48 h and at 6 months post stent implantation (104.6+/-4.8 vs 89.2+/-3.4, p<0.01, 109.6+/-11.2 vs 98.5+/-5.0, p<0.05). The study concludes that MCP-1 production at stented coronary arterial sites is associated with an increased risk for restenosis post stent implantation.