The purpose of this study was to examine differences in the changes in levels of differentiation, as measured by the Differentiation of Self Inventory (DSI) (Knauth & Skowron, 2004), that occurred among high school students who participated in a semester-long (n = 69) and year-long (n = 119) AFS (formerly known as American Field Service) program and a control group (n = 75) that did not study abroad. Gender of student and level of individualism of host country were also examined. The DSI full scale and four subscales: emotional reactivity, I position, emotional cutoff, and fusion with others were used to assess levels of differentiation. This study was a non-equivalent control group experimental pretest-posttest design. Pretest scores were used as the covariate in the posttest ANCOVA. Results revealed that female students who studied abroad for both one year and one semester experienced significant increases in levels of differentiation as measured by the DSI full scale versus female students who did not study abroad. There were no significant differences among males who studied abroad for one year, one semester or not at all. Additional results indicate a significant difference in changes in level of differentiation, as measured by the DSI full scale, between genders in the control group and the semester abroad group. Additional gender differences were revealed on the emotional reactivity and fusion with others subscales. Level of host country's individualism was not a significant factor. Results support previous literature which states that males and females engage in differing processes when forming their identity. Results also demonstrate that studying abroad is a meaningful life experience significant enough to assist females with increasing levels of differentiation. Additional results, a discussion of the results, limitations, and implications for practice and research are also provided. / Ph. D.