A syndrome of periodic fever that resembles human cyclic neutropenia in its clinical presentation has been identified in 12 children observed at two major referral centers. Attacks characterized by abrupt onset of fever, malaise, chills, aphthous stomatitis, pharyngitis, headache, and tender cervical adenopathy occur at 4- to 6-week intervals over periods of years. These episodes of illness resolve spontaneously in 4 to 5 days. Mild leukocytosis and elevation of the erythrocyte sedimentation rate during attacks are the only laboratory abnormalities. Affected children grow normally, are not unusually susceptible to infection, and exhibit no long-term sequelae. Attacks may be aborted by short courses of prednisone but do not respond to nonsteroidal anti-inflammatory agents. This syndrome is sporadic and appears to be much more common than cyclic neutropenia.