Rumination—repetitively thinking about one’s emotional state, its causes and consequences-exacerbates negative mood and plays an important role in the aetiology and maintenance of depression. Yet, it is unclear whether increased vulnerability to depression is associated with simply how much a person ruminates, or the short-term impact rumination has on a person’s negative mood. In the current study, we distinguish between the level versus the impact of rumination, and we examine how each uniquely predicts changes in depressive symptoms over time in an undergraduate sample. Using experience sampling, we assessed students’ (N = 101) subjective experiences of positive and negative affect and their use of rumination and distraction in daily life for seven days. Participants also reported their depressive symptoms before and after the experience sampling. Increases in depressive symptoms over the week were predicted by how much people ruminated, but not by its impact on negative mood.