Between June 1986 and October 1992, disseminated toxoplasmosis was diagnosed in 16 AIDS patients. 13 cases were diagnosed at autopsy where multiple organ involvement was documented in all 13. Three patients were diagnosed intra vitam. All 3 survived with appropriate treatment. Clinical features indicative of disseminated toxoplasmosis were: fever of unknown origin between 39 degrees and 40 degrees C in 16 cases, clinical signs suggestive of sepsis or septic shock in 15, with progression to multiorgan failure in 10, disseminated intravascular coagulopathy in 6, confusion, disorientation or apathy in 13 and lack of a systemic pneumocystis carinii prophylaxis in all 16. Typical laboratory markers were: CD4 cell counts below 100 x 10(6)/l in 16 cases, elevation of serum lactic dehydrogenase in 16 and creatine phosphokinase (in 4/6), normal or only slightly elevated C-reactive protein (in 9/11), positive Toxoplasma gondii IgG antibodies in 15/16 and negative IgM antibodies in all 16. Lesions indicative of cerebral toxoplasmosis were visualized on cranial computerized tomography in only 3/10 evaluated patients. In patients with advanced HIV infection presenting with a systemic illness, including the clinical and laboratory features described above, systemic Toxoplasma gondii infection must be included in the differential diagnosis. In these patients, specific and if warranted, invasive diagnostic procedures followed by early vigorous therapeutic intervention should be considered.