The authors tested the effects of cues to action--messages intended to increase flu immunizations. North Dakota counties were randomly assigned to reminder letters, action letters, or no letters. Within the reminder-letter counties, Medicare recipients received either (a) a reminder from the state peer review organization (PRO) to obtain a flu shot or (b) a reminder from the PRO, framed either in terms of the loss associated with failing to get a shot or (c) the benefits associated with getting a shot. Within the action-letter counties, Medicare recipients leaned where and when to receive a flu shot. Reminder type failed to differentially affect the immunization rate (overall M = 24.5%). However, the action messages worked better (28.2%) than no message (19.6%).