Familial periodic fever syndromes, otherwise known as hereditary autoinflammatory syndromes, are inherited disorders characterized by recurrent episodes of fever and inflammation. The general hypothesis is that the innate immune response in these patients is wrongly tuned, being either too sensitive to very minor stimuli or turned off too late. The genetic background of the major familial periodic fever syndromes has been unraveled, and through research into the pathophysiology a clearer picture of the innate immune system is emerging. After an introduction on fever, interleukin-1 and inflammasomes, which are involved in the majority of these diseases, this manuscript offers a detailed review of the pathophysiology of the cryopyrin-associated periodic syndromes (CAPS), Familial Mediterranean Fever (FMF), the syndrome of pyogenic arthritis, pyoderma gangrenosum and acne (PAPA), Blau syndrome (BS), TNF-receptor associated periodic syndrome (TRAPS) and hyper-IgD and periodic fever syndrome (HIDS). Despite recent major advances, there are still many questions to be answered regarding the pathogenesis of these disorders.