The cases of 51 patients with malaria seen at the Albert Einstein College of Medicine hospitals from January 1986 to June 1991 are reviewed. Thirty-five patients acquired infection on journeys to their country of origin. Of these 35 patients, 83% of whom had lived in the United States for > or = 2 years, only 17% received antimalarial prophylaxis. Ten of the 51 patients were born and raised in the United States, and 70% received prophylaxis (P < .01). Six of the 51 patients were visitors to the United States from areas endemic for malaria. Overall, 64% of patients acquired malaria in West Africa, south of the Sahara; 20% in Asia; 8% in Ecuador; 6% in Haiti; and 4% in the Middle East. The majority of infections were due to Plasmodium falciparum. Six patients traveled to a zone endemic for malaria while pregnant, and none received prophylaxis. In nine of 13 patients who received prophylaxis, there was inadequate dosing or poor compliance. Individuals born in regions endemic for malaria are at high risk of acquiring malaria on return to their countries of origin and are less aware of the need for malaria prophylaxis than are other travelers.