Purpose: The aim of this study was to examine patients with Chronic Hepatitis B (CHB) and their level of knowledge of their disease, uncertainty, stress and health behaviors and to identify factors influencing their health behavior. Methods: A cross-sectional, descriptive design was used. The sample included 136 patients in a gastroenterology outpatient department at one hospital located in Seoul. The mean age of the subjects was 41 and 77.2% were male. Data were collected using a structured questionnaire from April to June 2009. The collected data were analyzed using SPSS/WIN 15.0. Results: The reported scores for knowledge of the disease, uncertainty, stress, and health behaviors were 14.43, 81.50, 26.50, 52.11, respectively. There were statistically difference between health behaviors and gender, age, marital status and antivirus treatment. A positive correlation existed between knowledge of disease and health behaviors (r=.199, p=.020). In contrast, there was a negative correlation between uncertainty and health behaviors (r=-.250, p=.003). The factors influencing health behaviors were knowledge of disease, gender, age, uncertainty, antivirus treatment, and marital status ($R^2$=.267, p<.001). Conclusion: These findings support that strategies for enhancing knowledge of disease and reducing uncertainty are needed to promote health behavior in patients with CHB.