We report 28 patients (20 male) with a syndrome characterized by abrupt onset of fever, malaise, aphthous stomatitis, tonsillitis, pharyngitis, and cervical adenopathy (PFAPA syndrome). Episodes of fever occurred at intervals of 5.1 +/- 1.3 weeks beginning at the age of 4.2 +/- 2.7 years. Fever, malaise, tonsillitis with negative throat cultures, and cervical adenopathy were reported in all 28 patients, aphthae in 19, headache in 5, abdominal pain in 5, and arthralgia in 3. Mild hepatosplenomegaly was observed in 6 patients. Mild leukocytosis, elevation of the erythrocyte sedimentation rate, and fibrinogen were found during attacks. These episodes of illness resolved spontaneously in 4.3 +/- 1.7 days. Serum IgD was found elevated (>100 U/mL) in 12 of the 18 patients tested (140.2 +/- 62.4 U/mL). Affected children grow normally, have no associated diseases, and have no long-term sequelae. Attacks were aborted by a single dose of oral prednisone (2 mg/kg) at the beginning of the attack in all 15 patients in whom this medication was prescribed. In 9 patients the syndrome has completely resolved (beginning at the age of 2.9 +/- 1.3 and lasting 8 +/- 2.5 years). In 3 other patients complete resolution of the attacks occurred after tonsillectomy was performed. PFAPA is sporadic, and no ethnic predilection was found. Increased awareness of the clinical syndrome has resulted in more frequent diagnosis and adequate treatment.