INTRODUCTION: Etiological evaluation of stroke in young patient includes different tests. It is important to determine the cause of stroke to plan treatment according to the etiological investigations and to reduce the risk of recurrence. We aimed to investigate the prothrombotic gene mutations in young patients with stroke and to compare the presence and absence of predisposing risk factors in terms of gene mutations. METHODS: Patients aged 18-45 years with ischemic stroke were included. Protein C (PC), protein S (PS), antithrombin3 (ATIII), homocysteine, antinuclear antibody (ANA) anticardiolipin (ACA) tests and Factor V G1691A Leiden (FVL) genetic test results of prothrombin G20210A, methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C were recorded. RESULTS: A total of 120 (64M, 56F) patients were included. The mean age of the patients was 38±6.9. Stroke risk factor was determined in 77 patients and 43 were not detected. Smoking was the most common in 44 (36.7%) and hypertension was recorded in 23 (19.2%) patients. FVL polymorphism was heterozygous in 13 patients. Prothrombin polymorphism 11 heterozygous, 1 homozygous, MTHFRC677T 56 heterozygous, 10 homozygous, MTHFRA1298C polymorphism 45 heterozygote, 13 homozygous was detected. Hyperhomocysteinemia 66, ATIII deficiency 16, PC deficiency 19, PS deficiency was detected in 19 patients. There were no significant differences in the heterozygous and homozygous polymorphisms of the prothrombotic gene in the group with and without predisposing risk factors. In addition, frequency of hyperhomocysteinemia, frequency of ATIII, PC, PS deficiency and frequency of ANA positivity were not significantly different between these two groups. DISCUSSION and CONCLUSION: The prevalence of MTHFR C677T and A1298C heterozygous polymorphism was found to be high.There was no significant difference between patients with stroke according to the presence of predisposing risk factors in terms of prothrombotic mutations. It was determined that the protombotic gene mutations did not affect the risk of stroke according to the presence of stroke risk factors.