The role of viral agents in the pathogenesis of inflammatory rheumatismal diseases is under debate. The purpose of this study was to investigate the role of the viruses Herpes Simplex Virus type1 (HSV-1) and type2 (HSV-2), Epstein-Barr Virus (EBV), Cytomegalovirus (CMV), and Human Herpes Virus-6 (HHV-6), and Human Parvovirus B19 in ankylosing spondylitis (AS) and Behcet's syndrome (BS). Between October 2005 and June 2007, 83 AS and 50 BS patients who were newly diagnosed at the Rheumatology Clinic were included into the study. Fifty individuals were selected as the control group. The presence of antibodies against the viruses HSV-1, HSV-2, EBV, CMV, HHV-6, and Parvovirus B19 was examined by microenzyme immunoassay (micro-ELISA) method. There was no statistically significant difference between the patients and the control group (p>0.05). Antibody positivity of each viral agent was found more in AS patients than in BS patients, however this difference was not statistically significant (p>0.05). According to the results of this study, the consumption that HSV-1, HSV-2, EBV, CMV, HHV-6 and Parvovirus B19 have role in the etiology of AS and BS has not been supported.