To receive actual information about the clinical course of falciparum malaria case history of 373 patients hospitalized in Chemin de Fer Hospital in Phnom Penh from May 1 till October 1, 1985 were evaluated. No patients were infected in Phnom Penh. We estimated that only 8.3% of patients had higher parasitaemia than 100,000 or more asexual parasites in microliter of peripheral blood which is considered as a heavy infection. Complicated malaria was found in 39 patients (10.4%). The most frequent complications were cerebral complications (80.0%), renal failure (23.3%), and liver failure (16.6%). Ten patients had multiple organ complications and they represented 25.6% of patients with complications. The 100% mortality was observed in those in coma stage III; with haemoglobinuria, epistaxis and melena. Only coma stage III as a single symptom caused the death. In other cases death resulted from multiple organ complications.