Objective: Globally, about 50 to 100 million patients are infected with dengue fever per year and the average mortality rate is about 3.5 to 5% in Asia. Because of appropriate geographic location and cultural factors, dengue fever has been the important subject of infectious disease that Taiwan faces. In order to control and prevent the spread of dengue fever effectively, how to diagnose the suspected case correctly by the clinical symptoms and to improve the early reporting rates become critical research questions. The purpose of this study is to explore the correlation between clinical symptoms and diagnosis of dengue fever, and the factors associated with being reported at the first outpatient visit among confirmed case by using Dengue Fever Survey Form, which including demographics, clinical symptoms, level of the first outpatient visit and whether the patient is reported at the first outpatient visit. Design: 593 virologically confirmed cases during 2006 Dengue endemics in Kaohsiung city were studied. The data were from Dengue Fever Survey Form, which were collected from January 1 to December 31,2006. Result: The mean age of cases was 46.45¡Ó19.06 years (range 2 years to 89 years). The most common symptoms were fever (97.3%), pain (75.2%), GI symptoms (74.7%), skin rash (49.2%), and thirsty/dry mouth (49.1%). Chi-square tests showed gender, age in group, viral type, whether dengue hemorrhagic fever or not, level of the first outpatient visit, pain and gastrointestinal symptoms were significantly associated with being reported at the first outpatient visit. The result of the analysis of logistic regression indicated that the significant predictors of being reported at the first outpatient visit were gender, age in group, viral type, level of the first outpatient visit, gastrointestinal symptoms and fatigue. Conclusion: Reporting of infectious disease is essential to detection of outbreaks, planning of control program and provision of appropriate treatment. Clinical symptoms of dengue fever and the level of the first outpatient visit will influence rates of being reported at the first outpatient visit. All medical providers involved in diagnosis and treatment of dengue fever should strengthen their knowledge by continuing learning in order to improve early identification rates. In addition, health department could try to improve the detection and reporting systems to make the reporting steps more convenient and advance early reporting rates.