Dengue fever (DF) has been endemic in Malaysia since 1902 and reached epidemic proportions in 1973. The incidence rate of the disease in 1973 was 5.4 cases per 100,000 and reached 10.4 cases per 100,000 in 1987. The Chinese are the main ethnic community affected showing an overall morbidity rate of 9.0 cases per 100,000 followed by Malays 2.9 cases per 100,000 and Indians 2.4 cases per 100,000. The ethnic race ratio between Chinese, Malays and Indians which was 3.7:1:1.3 in 1975 reached 3.7:1:0.9 in 1987. The attack rates were observed to be higher in the males. The mean male:female ratio among Chinese was 1.1:1, while for Malays and Indians it was 1.5:1. The age-specific morbidity rate was highest in the 10- to 19-year age group followed by the 20- to 29-year age group. Epidemics of dengue fever were found to occur seasonally with the appearance of two peaks, viz. one in June and the other in August. Dengue fever, a rural disease before, has established itself as an urban disease.