Periodic fever is defined as a series of unexplained febrile episodes, most often starting during childhood. The febrile episodes last usually few days, are of fixed or variable duration, and regress spontaneously, the intervals between episodes being asymptomatic. Fever is accompanied by clinical manifestations affecting peritoneal, pleural and/or mucous membranes, joints and skin. Four different etiologies are presently known. Three are hereditary diseases: familial mediterranean fever and periodic fever with hyperimmunoglobulinemia D which have a recessive autosomal transmission, and TNF receptor associated periodic syndrome or TRAPS which has a dominant autosomal transmission. One is sporadic: periodic fever with aphthous stomatitis, pharyngitis and adenopathy or PFAPA. Other etiologies are yet to be identified as many cases of periodic fever remain unexplained.