Fungi are the causes of an increasing number of fatal disseminated infections, especially those infections which occur as complications of myeloproliferative disease or of therapy with steroids or antimetabolites.1 With more attention being directed toward the identification of the infecting fungus, a growing number of ubiquitous fungi, previously presumed to be saphrophytic, are recognized to possess pathogenic potentiality.2Below is the report of a case of fungal infection in which an unusual saphrophyte in man,Penicillium, is implicated as the causative agent. It is the first reported case of fatal mycotic intracranial arteritis with aneurysm, the rupture of which was preceded by an eosinophilic cerebrospinal fluid (CSF) pleocytosis. Report of a Case An 11-year-old white boy with a history of numerous dental problems and "respiratory allergies" extracted a loose left maxillary deciduous tooth in September 1966, after which his left cheek and eyelid became swollen. Orally administered antibiotics elicited no