Background and Purposes: Until now, limited data are available about the potential effect of coexisting small vessel disease (SVD) on the long-term outcome of stroke patients with intracranial large artery atherosclerosis (ILAA). Methods: A prospective study was performed on 293 patients with symptomatic ILAA, who were divided into 4 groups (group I, single intracranial large artery atherosclerosis (SILAA) without SVD; group II, multiple intracranial large arteries atherosclerosis (MILAA) without SVD; group III, SILAA with SVD; group IV, MILAA with SVD) and followed up for recurrent stroke or death. Results: The 3-year cumulative risks of recurrent stroke were 18% for SILAA without SVD, 38% for MILAA without SVD, 21% for SILAA with SVD and 34% for MILAA with SVD. The 3-year cumulative risks of death were 6, 7, 20 and 22%, respectively. Compared with SILAA without SVD, more recurrent stroke occurred in MILAA without SVD (log-rank 3.83; p = 0.050) and MILAA with SVD (log-rank 7.79; p = 0.014), and the higher risk of death (log-rank 9.472; p = 0.002) was found in group MILAA with SVD. A Cox proportional-hazards regression model showed that MILAA with SVD may be a predictor of recurrent stroke (hazard ratio 2.001; 95% CI 1.108-3.934; p = 0.044), and a borderline predictor for death (hazard ratio 3.180; 95% CI 0.895-10.987; p = 0.073). Conclusion: Coexisting SVD is very common and may predict poor outcome in stroke patients with symptomatic ILAA. Copyright (C) 2010 S. Karger AG, Basel