Results are presented from the 1,000 slide-confirmed malaria cases seen during the period August 1979-September 1981 at San Lazaro Hospital, in Manila, Philippines; 56% were caused by Plasmodium falciparum, 38% by P. vivax, 6% were mixed infections, and 0.1% by P. malariae. The overall case fatality rate was 1%, all due to P. falciparum. Cerebral involvement occurred in 7% and the case fatality rate was 20% compared to a case fatality rate of 0.2% among P. falciparum cases without cerebral involvement. In vivo chloroquine-resistant P. falciparum was seen in 4% of the cases, but of those treated in 1981, 9% of the cases showed resistance. The distribution of chloroquine-resistant cases by province in the Philippines is shown, with resistance being reported for the first time from Isabela, Bulacan, Zambales, Rizal and Bataan provinces. Diagnostic, clinical, and epidemiologic aspects of the cases are discussed, as well as the trend in malaria cases over the last 20 years.