An outbreak of hemorrhagic dengue fever occurred in Cuba in 1981. Among a population of about 10 million people, 344.203 persons were affected; 71,3% of these were adults and the remaining were children. Among the latter the disease was more severe. During the peak of the epidemic up to 11. 701 cases were reported in one single day. In this article the organizational aspects of health care delivery durint the epidemics as well as the studies performed in the 2239 patients admited to 3 hospitals of the city of La Habana from June to August 1981 are reported. The most important clinical and laboratory data from sample of 2239 patients under 15 years of age are presented. Some therapeutic aspects, including the experience of the author with the use of in tereferon in 166 patients, are also discussed.