Objective:Our aim in this study is to reveal the frequency of febrile seizures in patients with Familial Mediterranean Fever and Periodic Fever, Aphthous stomatitis, Pharyngitis, cervical Adenitis syndrome and to compare it to normal population.Materials and Methods:Patients with Familial Mediterranean Fever and Periodic Fever, Aphthous stomatitis, Pharyngitis, cervical Adenitis syndrome, who were diagnosed according to Turkish pediatric Familial Mediterranean Fever diagnostic criteria and Marshall criteria, were enrolled to the study. A form containing questions about febrile seizures history was prepared for Familial Mediterranean Fever and Periodic Fever, Aphthous stomatitis, Pharyngitis, cervical Adenitis syndrome patients. Demographic data and febrile seizures history of Periodic Fever, Aphthous stomatitis, Pharyngitis, cervical Adenitis patients were obtained by calling the parents by phone. Familial Mediterranean Fever patients were randomly selected during their routine follow-up. The frequency of febrile seizures in both disease groups was compared with the prevalence of previous febrile seizures studies in the general population in Turkey.Results:A total of 417 Familial Mediterranean Fever and 152 Periodic Fever, Aphthous stomatitis, Pharyngitis, cervical Adenitis subjects were recruited to the study. The frequency of febrile seizures in Familial Mediterranean Fever and Periodic Fever, Aphthous stomatitis, Pharyngitis, cervical Adenitis syndrome was similar (8.4% vs. 8.6%; P > .05). The frequency of febrile seizures in Familial Mediterranean Fever and Periodic Fever, Aphthous stomatitis, Pharyngitis, cervical Adenitis syndrome patients was found to be significantly higher than the frequency in general population (8.4% vs. 4.4%) [P < .0001, OR: 1.99 (CI: 1.4-2.8)]; (8.6% vs. 4.4%) [P < .01, OR: 2.03 (CI: 1.1-3.6)], respectively.Conclusion:The frequency of febrile seizures in patients with Familial Mediterranean Fever and Periodic Fever, Aphthous stomatitis, Pharyngitis, cervical Adenitis syndrome was found to be significantly higher than in the general population. This increased frequency of febrile seizures in both periodic syndromes seems to be a result of recurrent fever.