 We will enroll in this study 17 subjects from the age of 4 years, including adults with active FMF despite colchicine therapy. Subjects will receive in random order two 3-month courses of Rilonacept at 2.2 mgkg maximum 160 mg by weekly subcutaneous injection and two 3-month courses of placebo injection. If patients have at least two FMF attacks during a treatment course they will be able to get if they choose the other treatment until the end of that treatment course. Our hypothesis is that Rilonacept will decrease the number of acute FMF attacks and will be safe to use. This study may confirm the importance of IL-1 in the cause of FMF. 