Self-control problems have recently received considerable attention from economic theorists. We conducted two studies to test the benefits of externally imposed deadlines and how willpower depletion affects behavior, providing some of the first data in these areas. Each study involved a behavioral intervention designed to affect performance. We find that for a lengthy task, regular deadlines neither reduce procrastination nor increase completion rates. Second, a willpower-depleting task reduces initial effort but increases overall task-completion rates. Our results help to inform ongoing efforts to understand and model procrastination, willpower and commitment mechanisms.