We report 78 cases of toxoplasmosis diagnosed between 1987 and 1992, from an autopsy study of 205 patients infected by the human immunodeficiency virus (HIV). Of the 78 patients 22 were females (28%) and 56 males (72%). Risk factors were as follows: intravenous drug addiction (44 cases, 56%), homosexuality or bisexuality (18 cases; 36%) and multiple blood transfusions (6 cases). Cerebral toxoplasmosis (CT) was diagnosed in 73 cases (93%) and was characterized by abscesses (59 cases), diffuse encephalitic lesions (8 cases), isolated cysts without inflammation (3 cases) and hemispheric involvement with ventricular hemorrhage (3 cases). Cerebral involvement were isolated (55/78 cases; 70%) or associated with multi-visceral diffusion (18/78 cases; 23%). Isolated extracerebral localization was observed in 5 cases. The most frequent extracerebral sites were: cardiac (21 cases), pulmonary (14 cases) and pancreatic (7 cases). Immunohistochemical study with anti Toxoplasma gondii antibodies allowed to a diagnosis of extracerebral localization in 8 cases. Ultrastructural features of Toxoplasma gondii were studied on post mortem myocardial samples (2 cases) open lung biopsy (1 case) and bladder biopsy specimen (1 case). Antemortem diagnosis of cerebral toxoplasmosis was performed on CT-scan in 59/73 (80%). Antemortem diagnosis of extracerebral toxoplasmosis was performed or suspected in 8/23 cases (34%): by isolation of trophozoites in bronchoalveolar lavage (2 cases), on an open lung biopsy (1 case) and on a bladder biopsy specimen (1 case), and by clinical and echocardiographic data (4 cases). Anti-toxoplasmic serology allowed to the diagnosis of toxoplasmosis in 12/78 cases (15%) by showing high levels of IgG in the serum.(ABSTRACT TRUNCATED AT 250 WORDS)