Background: Major clinical manifestations of antiphospholipid syndrome (APS) in the central nervous system are generally arterial thrombotic events and a number of non-thrombotic neurologic syndromes. Antiphospholipid antibodies (APAs) are one of the important risk factors for cerebrovascular accidents (CVA). The aim of present study was to assess the relationship between APA titers and CVA in this clinically important age group.Methods: This case-control study was carried out on patients under 50 years old who had CVA (stroke or transient ischemic attack) in Shahid Sadoughi Hospital in Yazd (central Iran) from Dec 2003 until March 2005. In this study, 61 patients with CVA were compared with 68 age- and gender-matched control subjects. Lupus anticoagulant assay results and APA titers were assessed in both groups.Results: The mean value of IgM APA titers in patients with cerebrovascular accidents was 6.492 MPL (IgM antiphospholipid units) and 1.846 MPL in the control group. The difference between the two groups was significant (p-value: 0.000). In 12 (20%) of the patients with cerebrovascular accidents, IgM titers were higher than 10 MPL, one of whom had an IgM titer higher than 40 MPL. The mean value of IgG titers in the case group was 5.50 GPL (IgG antiphospholipid units) and 3.51 GPL in the control group. The difference between the two groups was significant (p-value: 0.012). Thirteen (21%) patients with cerebrovascular accidents had IgG titers higher than 10 GPL. The difference between the LA assay results was not significant between the two groups (p-value: 0.311).Conclusion: The present study showed a positive relationship between APL (IgM and IgG) titers and CVA in patients under 50 years old.