The purpose of this dissertation was to examine the association between physical activity (PA) and screen time (television viewing, computer use, and video game playing) in college students. Paper 1 examined descriptive data on college students' PA habits and sedentary behaviors to assess if any evidence exists that may suggest displacement between PA and screen time. Male students were significantly more physically active than their female counterparts in terms of days per week engaged in aerobic exercise, strength training, and when categorized by stages of change. Male students also reported significantly higher levels of overall screen time and television viewing, whereas female students reported significantly higher levels of time engaged in homework. Regardless of gender or PA levels, when students were categorized according to their PA stage of change, there was no significant difference in the amount of television watched, which suggested that, within a collegiate population, television and PA are not competing behaviors. Paper 2 sought to determine the relationship among PA, television, computer use, and video game playing throughout a 24-hour period of time and within 4 distinct time blocks which reflect a typical day in the life of a college student. Students were given a 24-hour time diary to log PA and screen-time behaviors. Male students reported significantly higher levels of PA, television viewing, and video game use than females across a 24-hour time period. When the day was categorized by time blocks, males reported significantly greater amounts of time spent viewing television and playing video games across all four blocks of time than did females. In terms of PA, males reported higher amounts of exercise than females between 7:00 pm and 11:00 pm. Weak relationships existed between PA and screen time across both a 24-hour time period and when categorized by time block, regardless of gender. Implications of this dissertation suggest that, within a collegiate population, PA, television viewing, computer use, and playing video games are independent of each other and that no relationship exists between PA and any variable of screen time.