We evaluate the choices of elders across their insurance options under the Medicare Part D Prescription Drug plan, using a unique dataset of prescription drug claims matched to information on the characteristics of choice sets. We document that elders place much more weight on plan premiums than on expected out-of-pocket costs; value plan financial characteristics beyond any impacts on their own financial expenses or risk; and place almost no value on variance- reducing aspects of plans. Partial equilibrium welfare analysis implies that welfare would have been 27 percent higher if patients had all chosen rationally.