This paper presents the results of two natural field experiments at a dental clinic. Guided by a simple theoretical model, we exogenously vary deadlines and associated rewards for arranging checkup appointments. Our data show strong and systematic effects of deadlines on patients’ behavior. Imposing deadlines induces patients to act earlier and at a persistently higher frequency than without a deadline. We further document that individuals systematically respond to deadlines even if these are not tied to explicit rewards. Several of our findings suggest that individuals’ responses to deadlines are shaped by limitations in memory and attention. Our results illustrate that deadlines can be a powerful management tool to encourage timely task completion and to increase the cost effectiveness of performance-contingent rewards.