An unusual case of cerebral toxoplasmosis in an HIV negative 11 year old child is reported. Central nervous system disease was assessed immunohistochemically in a brain biopsy specimen with TgP8--a specific monoclonal antibody against Toxoplasma gondii antigens--thus confirming IgG and IgM serology, technetium scan findings, and clinical data. In addition, an active parasitaemia was confirmed by DNA in situ hybridisation assay in white cells using an ABGTg4 probe. The child recovered after specific T gondii treatment. Follow up six months later showed that he was immunodeficient.