Students often "multitask" with electronic media while doing schoolwork. We examined the effects of one form of media often used in such multitasking, instant messaging (IM). We predicted that students who engaged in IMing while reading a typical academic psychology passage online would take longer to read the passage and would perform more poorly on a test of comprehension of the passage. Participants were randomly assigned to one of three conditions (IM before reading, IM during reading, or no IM). We found that students took significantly longer to read the passage when they IMed during reading (not including time taken to IM) than in other conditions. However, test performance did not differ by condition. Students who are managing busy lives may think they are accomplishing more by multitasking, but our findings suggest they will actually need more time to achieve the same level of performance on an academic task.