Familial Mediterranean fever (FMF), which is the prototype of the hereditary periodic fever syndromes, is common in the countries around the Mediterranean Sea. Considering its geographical position in the northwest of Iran, with its population of Turkish origin and its vicinity to the Mediterranean Sea, th incidence of FMF should be high in Ardabil. The goal of this study was to introduce FMF as a disease with significant outbreak in this area. Based on the Tel-Hashomer criteria, patients suffering from FMF were collected from private clinics together with the medical records of adult and pediatric rheumatology clinics. Of 112 total patients determined, 74 were studied. All of the patients were interviewed and completed a questionnaire. Familial Mediterranean fever was common among children under 18 years (76%), and it was more common in males than females (M/F 1.17). Abdominal pain was the most common complaint (74%) and abdominal pain and fever (95% and 84%, respectively) were the main clinical symptoms. The average duration of pain was 12-72 hours and the average recovery (attack-free period) was from one week to one month (63.5%). The majority of the patients had hospital admission for diagnostic work-up (85%) and some (32%) ha undergone surgical operation erroneously; 92% of the patients had taken medications with incorrect diagnosis; and 20% had positive familial history of FMF. Fifty percent of the patients' parents were first-degree relatives an in 59.5% delay in diagnosis was more than three years. It seems that FMF is more common in the Northwest of Iran than previousl thought, although physicians are not familiar with it. The common age for manifestation of this disease is under 18 years and its presentation after the age of 40 years is very rare.