A series of structural equation models are presented that capture relationships among sociodemographics, activity participation (time use), and travel behavior for each day during a week in a developing country (Korea). Complex and strong relationships among the endogenous and exogenous variables are explained. In addition, results are similar to findings in the existing literature in developed countries such as European countries and the United States. It is temporarily concluded that there are similar relationships between sociodemographics and travel behavior in developing and developed countries. It is also confirmed that activity patterns are significantly different on weekdays and weekends. Furthermore, during weekdays there are some day-to-day variations in the patterns of activity participation and travel behavior. Finally, the relationships among sociodemographics, activity participation, and travel behavior from the direct, indirect, and total effects in structural equation model systems are presented and explained. This study may contribute to an understanding of travel behavior in developing countries.