Hwa-Byung, known as an anger illness, was conceptualized in Korean culture and listed in the glossary under Culture-Bound Syndromes in the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994). Hwa-Byung develops when the emotions of anger have been suppressed for a long period of time and it becomes difficult to control those feelings. Common complaints of Hwa-Byung have two dimensions, psychological and physical symptoms. The prevalence of Hwa-Byung exhibits gender differences in that the majority of individuals who experience Hwa-Byung are women between the ages of 40 and 60. However, as the number of Korean immigrants in the United States continues to increase and their issues draw attention from researchers, the topic of Hwa-Byung receives little. Because Korean immigrants in the United States share a cultural background with their origin of ethnicity, and at the same time, may also assimilate the American culture during the acculturation process, this study will address the cultural differences in Hwa-Byung between native Koreans who live in South Korea and Korean immigrants in the United States. Accordingly, the purpose of this study was to examine the differences and similarities of Hwa-Byung in native Korean middle-aged women in South Korea and Korean immigrants in the United States, roughly between the age range of late-30's to middle 60's, by investigating the influencing factors of stressful life events, stress response, anger expression, and demographic background. A sample size of at least 200 participants, required for each group, using both paper-pencil and web-based methods, depended on participants' preferences, which were influenced by a gap in ages and the level of familiarity with and/or ability to access Internet. Participants were randomly selected from major cities, both in South Korea (including Seoul, Incheon, Busan, Daejeon, and Gyeonggi Province) and the United States (including Chicago, New York, and Los Angeles), using similar proportions of ages for both groups for the equivalences of participants in cross-cultural research. Survey measures included five instruments: (a) the Hwa-Byung scale (Kwon, Kim, Park, Lee, Min, & Kwon, 2008); (b) Life Stress for Korean women (Chon & Kim, 2003); (c) stress response inventory (SRI) (Koh, Park, & Kim, 2000); (d) anger expression (Hahn, Chon, Lee, & Spielberger, 1997), and (e) demographic background that measured the variables used in this study. To minimize the weakness of language differences used in the different cultural contexts, survey packages for Korean immigrant participants in the United States were formatted in both Korean and English for each item. Thus, a translation process became necessary, especially for the Korean instruments of the Hwa-Byung Scale, Life Stress for Korean women and Stress Response Inventory (SRI), from Korean into Englishtwo of which were (originally developed by Korean researchers) . On the other hand, native Koreans submitted only the Korean version of questionnaires because they fully understood the meaning of questionnaire statements, as well as in order to get rid of possible distractions by the inclusion of English sentences.