Recent dengue outbreaks in the Caribbean and Central and South America and the presence of competent mosquito vectors increase the likelihood of future autochthonous transmission in Florida. During April 1997 to March 1998, a laboratory-based active surveillance program detected 18 cases of dengue involving all four dengue serotypes. All patients reported recent travel to countries with indigenous dengue transmission. These results demonstrate that dengue infections are imported into Florida at a much higher rate than reflected by previous passive surveillance; therefore, the risk for local dengue transmission may be increasing.