In my dissertation I analyze how time constraints influence research in different areas of science. I use two case studies, gravitational wave physics and translational medicine, in order to develop an account of time-sensitivity in science, which I take to be a judgment about a desired or expected time-frame of having a result. The degree of time-sensitivity gives rise to concerns about efficiency and influences methodological choices, especially the epistemic trade-offs between speed and accuracy. Translational medicine is dedicated to accelerating the process from discovery to implementation in practice because the deliverances of medicine are urgently expected in the society. I identify some epistemological and ethical problems for the acceleration of medical research. Gravitational wave physics doesn’t have such a straightforward societal pressure to deliver results quickly, but it nonetheless has ends in sight and time constraints that influence research on different levels: of goal setting, methodology, and the communication of results. Another issue I discuss is the notion of urgency. What are the social and the epistemic sources of urgencies in science, and how are they prioritized? What kind of epistemic trade-offs do urgencies require?