The aim of this study was to investigate the time course of angiographic restenosis rate and late loss after successful percutaneous coronary intervention and vascular brachytherapy with beta-irradiation using strontium-90/yttrium-90 in 98 patients who were prospectively enrolled into a quantitative angiographic and clinical follow-up protocol at 6, 12, and 24 months after the index procedure, regardless of their symptom status. Actuarial restenosis rates measured 11.2 +/- 5% at 6 months of follow-up, 24.5 +/- 5% at 12 months, and 28.5 +/- 6% at 24 months, respectively. Late loss of the stent segment during the first 6 months measured 0.38 +/- 0.40 mm (6 to 12 months: 0.25 +/- 0.38 mm; 12 to 24 months: 0.16 +/- 0.32 mm), of the injured segment 0.27 +/- 0.21 mm (6 to 12 months: 0.21 +/- 0.26 mm; 12 to 24 months: 0.13 +/- 0.24 mm), of the irradiated segment 0.18 +/- 0.29 mm (6 to 12 months: 0.19 +/- 0.31 mm; 12 to 24 months: 0.11 +/- 0.27 mm), and of the analysis segment 0.18 +/- 0.36 mm (6 to 12 months: 0.17 +/- 0.29 mm; 12 to 24 months: 0.11 +/- 0.20 mm). Restenosis after angioplasty and beta-irradiation of in-stent restenotic lesions is not complete within 6 months but is sustained with a gradual decrease over 24 months.