A 24-year-old woman with acquired immunodeficiency syndrome was admitted with septic fever of unknown origin and a 2-week history of diarrhea. Clinical diagnostic procedures did not reveal the cause of sepsis. Broad-spectrum antibiotics and intensive symptomatic therapy could not prevent progressive deterioration. The patient developed septic shock and consumptive coagulopathy and died 6 days after admission. Autopsy revealed disseminated infection with toxoplasma gondii and multiple organ manifestations. We conclude that disseminated toxoplasmosis should be considered in AIDS patients with septic disease of unknown origin. Extremely elevated lactate dehydrogenase may suggest disseminated toxoplasma gondii infection. New procedures such as polymerase chain reaction for detection of toxoplasmosis may be helpful diagnostic tools.