Background and Purpose: Factor (F) XIII is a transglutaminase which stabilizes fibrin clots by forming cross-links between chains of fibrin. A common Val34Leu polymorphism of FXIII is correlated with the level of activated plasma FXIII. The homozygous 34Val genotype may be associated with an increased risk for thrombosis by forming fibrin fibers more resistant to fibrinolysis. The aim of the study was to investigate the association between the FXIII Val34Leu polymorphism and the risk of ischemic stroke due to small vessel disease (SVD) or the risk of primary intracerebral hemorrhage (PICH). Methods: 66 patients with SVD stroke and 135 age- and sex-matched controls as well as 64 patients with PICH and their 127 controls were included. The FXIII Val34Leu polymorphism was genotyped using the polymerase chain reaction and restriction enzyme digestion methods. Results: The homozygous 34Val genotype was found significantly more often in patients with SVD stroke than in their controls (62 vs. 42%). On multivariate analysis, the Val/Val genotype was associated with an increased risk of SVD stroke (odds ratio: 2.1, 95% confidence interval: 1.1–3.9). The genotype distribution did not differ significantly between PICH patients and their controls (50 vs. 43%). Conclusion: Our results suggest that the Val/Val genotype of FXIII could be associated with an increased risk of SVD stroke.