Backgrouds: Intracoronary thrombosis after drug-eluting stent (DES) implantation is not well understood. Therefore, we investigated its incidence and determinants using optical coherence tomography (OCT). Methods: OCT was performed in 226 patients (total DESs, n = 244; sirolimus-eluting stent [SES], n = 95; paclitaxel-eluting [PES], n = 62; zotarolimus-eluting stent [ZES], n = 87) after implantation (mean, 11 months; range, 3–66 months). Results:Intracoronary thrombus was detected in 35 (14%) cases (27 SES [28%], 7 PES [11%], 1 ZES [1%]; P < 0.001), and was associated with longer stents, smaller stent diameter, and stents at bifurcation lesions. More struts without neointima (26짹23 vs 8짹17, P < 0.001) and malapposed stent struts (6짹14 vs 2짹6, P < 0.001) were also associated with thrombosis. Multiple logistic regression analysis found the following determinants of intracoronary thrombosis: stent ���28 mm (odds ratio [OR], 7.31; 95% CI, 1.79–29.86, P = 0.01], stent diameter <3.0 mm (OR, 4.38; 95% CI, 1.38–13.97; P = 0.01), and ���8 struts without neointima in each stent (OR, 3.29; 95% CI, 1.07–10.17; P = 0.04). Conclusion: Length, size, and types of DES may be more important than clinical factors in intracoronary thrombosis after DES implantation.