We describe PRioritized EPidemic (PREP) for routing in opportunistic networks. PREP prioritizes bundles based on costs to destination, source, and expiry time. Costs are derived from per-link "average availability" information that is disseminated in an epidemic manner. PREP maintains a gradient of replication density that decreases with increasing distance from the destination. Simulation results show that PREP outperforms AODV and Epidemic Routing by a factor of about 4 and 1.4 respectively, with the gap widening with decreasing density and decreasing storage. We expect PREP to be of greater value than other proposed solutions in highly disconnected and mobile networks where no schedule information or repeatable patterns exist.