Aedes aegypti is an important vector for dengue fever (DF) and dengue shock syndrome (DSS). In order to study the density fluctuation of Ae. aegypti, 42, 43, and 60 ovitraps were set in cities of Tainan, Kaohsiung and Taitung, respectively. Surveillance of vector for Tainan and Kaohsiung was carried out from April through December in 2002. Survey in Taitung was made from October to November. Eggs or larvae in each ovitrap were collected weekly and examined in the laboratory until adult emerged. Results of egg examination showed that increase of eggs started from June both in Tainan and Kaohsiung, this indicates that vector density was associated with the precipitation. The peak of eggs of Aedes was found in June in these two cities. The increase of eggs also found to be correlated with the rising of temperature. In Tainan, the number of Ae. aegypti was more than that of Ae albopictus except June to August.
