A physically healthy young woman who suffered from a prolonged attack of mania increasing in severity, died a sudden clinically unexplained death. Post-mortem examination revealed a circumscribed glioma (spongioblastoma polare) in the right diencephalo-mesencephalic area. The case is discussed in the light of similar previous observations. Certain points in the technique of the examination of the central nervous system in cases of sudden unexplained death are stressed.Abstract Teaser