There are four species of Plasmodium that cause malaria in humans: P. vivax, P. malariae, P. falciparum, and P. ovale. All are transmitted by the bite of an infected female anopheles mosquito. P. falciparum is most likely to cause severe disease in humans including cerebral malaria, profound anemia, waxing/waning fevers, and, possibly, death. Clinical manifestations include paroxysms representing the erythrocytic stage of rigors: severe febrile episode, defervescence, and diaphoresis. The white blood cell count may be normal or slightly decreased. Blood cultures are not helpful. The diagnosis is established by visualization of the parasite on a thin or thick peripheral smear. However, smears may be negative secondary to RBC sequestration and treatment should be initiated if malaria is clinically suspected. Malaria may be managed as an outpatient with oral chloroquine if infection is not due to P. falciparum. Patients with P. falciparum infection or greater than 3% parasitemia should be hospitalized and treated with oral quinine and doxycycline or intravenous quinidine (intravenous quinine is not available in the United States).