Approximately 90% of patients with familial Mediterranean fever (FMF) complain of recurrent attacks of fever and abdominal pain of various severities. Prior to the diagnosis of FMF, the majority of patients are admitted to emergency units with a suspicion of acute abdomen pain and at least half of them undergo unnecessary abdominal interventions. The purpose of this study is to determine the frequency of FMF among the patients who are admitted to emergency units for acute abdominal pain. One hundred consecutive patients who were admitted to an emergency unit in Istanbul, Turkey, with acute abdominal pain were screened for FMF. When the definite cases were considered, a frequency of 2% was encountered which was significantly high. compared to the frequency of FMF in Turkey. Physicians working in emergency units should include FMF in their differential diagnosis list when evaluating a patient with acute abdominal pain, especially in countries where the disease is prevalent.