Stent thrombosis is a catastrophic occurrence burdened by a high mortality rate and a tendency to recur. We sought to evaluate the angiographic risk factors for recurrent stent thrombosis (rST) in a subpopulation of 91 Outcome of PCI for stent-ThrombosIs Multicenter STudy (OPTIMIST) patients who underwent quantitative angiographic evaluation by an independent core laboratory. The Academic Research Consortium criteria were used for rST adjudication. A multivariate Cox proportional hazards model was applied to estimate the hazard ratios and the corresponding 95% confidence intervals for the occurrence of Academic Research Consortium-defined, definite rST (primary end point), definite or probable rST (secondary end point), and definite or probable or possible rST (secondary end point). A total of 8 definite rST events occurred during a median follow-up of 244 days (range 165 to 396), of which 5 were early and 3 were late. In the multivariate model, a residual thrombus score of > or =3 (hazard ratio 6.5, 95% confidence interval 1.4 to 30.7, p = 0.017) and a larger postprocedural reference vessel diameter (hazard ratio 4.5, 95% confidence interval 1.5 to 13.3, p = 0.006) were significantly associated with the primary end point. When the same model was applied to the 15 definite and probable rST events, only a residual thrombus score of > or =3 (hazard ratio 7.8, 95% confidence interval 2.5 to 24.5, p <0.001) was significantly associated with rST. Finally, when possible rST events were included (18 patients), a residual thrombus score of > or =3 remained associated with the dependent variable (hazard ratio 6.1, 95% confidence interval 2.0 to 18.2, p = 0.001), along with a larger postprocedural reference vessel diameter. In conclusion, when performing percutaneous coronary intervention for stent thrombosis, the residual thrombus burden and larger reference vessel were potent risk factors for rST.