Title: Coverage as a Principle for Discovering Transferable Behavior in Reinforcement Learning. Abstract: Designing agents that acquire knowledge autonomously and use it to solve new tasks efficiently is an important challenge in reinforcement learning. Unsupervised learning provides a useful paradigm for autonomous acquisition of task-agnostic knowledge. In supervised settings, representations discovered through unsupervised pre-training offer important benefits when transferred to downstream tasks. Given the nature of the reinforcement learning problem, we explore how to transfer knowledge through behavior instead of representations. The behavior of pre-trained policies may be used for solving the task at hand (exploitation), as well as for collecting useful data to solve the problem (exploration). We argue that pre-training policies to maximize coverage will result in behavior that is useful for both strategies. When using these policies for both exploitation and exploration, our agents discover solutions that lead to larger returns. The largest gains are generally observed in domains requiring structured exploration, including settings where the behavior of the pre-trained policies is misaligned with the downstream task.