Hypotheses generated by the precaution adoption process model, a stage model of health behavior, were tested in the context of home radon testing. The specific idea tested was that the barriers impeding progress toward protective action change from stage to stage. An intervention describing a high risk of radon problems in study area homes was designed to encourage homeowners in the model's undecided stage to decide to test, and a low-effort, how-to-test intervention was designed to encourage homeowners in the decided-to-act stage to order test kits. Interventions were delivered in a factorial design that created conditions matched or mismatched to the recipient's stage (N = 1,897). Both movement to a stage closer to testing and purchase of radon test kits were assessed. As predicted, the risk treatment was relatively more effective in getting undecided people to decide to test than in getting decided-to-act people to order a test. Also supporting predictions, the low-effort intervention proved relatively more effective in getting decided-to-act people to order tests than in getting undecided people to decide to test.