Objective: The authors explored associations among types of physical activity and hopelessness, depression, and suicidal behavior among college students. Participants: Participants included 43,499 college students aged 18 to 25 who completed the 2005 National College Health Assessment conducted by the American College Health Association. Methods: The authors used logistic regression modeling to compare the odds of experiencing hopelessness, depression, and suicidal behavior in students who engaged in various levels of aerobic and strength or toning activity with students who did not perform these activities. Results: Men and women who engaged in some physical activity each week demonstrated a reduced risk of hopelessness, depression, and suicidal behavior compared with their inactive counterparts. Conclusions: This study provides empirical evidence that establishes the association between physical activity, especially aerobic activity, and reduced risk of hopelessness, depression, and suicidal behavior among college students. (Contains 5 tables.)