Agrowing body of literature indicates that affective states can influence cognitive processes. The core assumption of Ellis and Ashbrook's (1988) model explaining these emotional after-effects on cognition is that the emotional state regulates the allocation of processing resources. A negative emotional state is supposed to pre-empt capacity normally allocated to the cognitive task at hand. This is assumed to occur because the negative emotional state leads to an increase in intrusive, irrelevant thoughts, which compete with relevant cognitive activities and thus result in a lack of attention given to relevant features of the task to be performed. In the present study, the hypothesis that negative emotions lead to a reduced information-processing capacity and that this is observable on a very basic level of information processing is tested. Therefore, 102 participants were assigned to three independent groups, each inducing one of a negative, a positive, or a neutral mood by means of a 3-minute video-clip. Shortly after the video-clip, two acoustical stimuli with increasing information were presented, while the P3 component of the event-related brain potential on these stimuli was measured as a psychophysiological indicator of cognitive resource allocation. In addition, the expenmental manipulation was checked by assessing subjective and external mood ratings as well as cortical alpha activity. Results show that the videos did in fact induce positive, neutral, or negative mood. Moreover, even when controlling for video-related unspecific cortical arousal, a significant emotional after-effect was found on the P3 component of the event-related brain potential, indicating reduced information-processing capacity, particularly in the negative mood condition. The reported data support Ellis and Ashbrook's model of emotional after-effects on cognitive processes. As those effects were observable after an event that did not demand a high amount of cognitive resources, this suggests that even tasks that do not heavily engage central processing resources and are not likely to be influenced by cognitive strategies, seem to be affected by a negative emotional state.