We presented our surveillance results on imported dengue cases in Taiwan during 2003-2007. A total of 542 imported dengue patients were identified. The travelers were infected in 17 countries in Southeast Asia, the Indian subcontinent, East African islands, South Pacific islands, and Central America. Most of these imported cases were infected in Southeast Asian countries. Phylogenetic analyses were conducted to examine 288 imported dengue virus (DENV) strains introduced from 13 countries. The results provide an updated view on the geographic distribution and dynamic transmission of epidemic DENV stains circulated in Southeast Asian countries. Although the geographic distributions of genotypes of DENV-3 isolated from Southeast Asian countries remain unchanged, the introductions and local expansions of epidemic DENV-1, DENV-2, and DENV-4 strains into new areas in Asia were observed. These findings highlight the importance to strengthen laboratory-based dengue surveillance for better understanding of transmission dynamics and molecular evolution of DENVs.