The case-reports of seventeen patients who experienced onset of systemic juvenile arthritis between the neonatal period and the age of ten months are studied. Group I consists of six cases in which onset took place after the age of five months. The condition progressed towards recovery with minimal residual joint disease, towards polyarticular involvement or towards perennial systemic manifestations. Group II individualizes three patients with neonatal manifestations, and chronic polymorphonuclear cell meningitis and major radiologic changes as typical features. The eight patients in Group III, some of whom had neonatal onset, exhibited febrile exacerbations with involvement of skin, joints and lymph nodes, often produced by various antigenic stimulations (infections, immunizations, gammaglobulin injections and delayed hypersensitivity reactions). In group III exacerbations were often shorter but more frequent than in group I. After several years follow-up, clinical and radiological evaluation showed no signs of residual joint disease in this group. Biological features in each of the three groups were manifestations of major non-specific inflammation. Histologic examination of lymph nodes and skin showed no specific abnormality. IgA and IgD concentrations were especially high in group III. The reality of the syndrome described many years ago by Wissler and Fanconi appears to be open to debate in the light of manifestations recorded in group III.