The effects of choice and predictability information regarding preparation for a barium enema procedure was investigated for patients differing in desire for control (DFC) and in experience with the barium enema exam. One-third of the patients, randomly assigned to the choice condition, were selected from three equally effective preparations. For these patients, choice and predictability information are confounded. Patients in the instruction only and information conditions were yoked to choice patients to control for type of preparation. Patients in the information condition were given the same sensation information about their specific preparation as those in choice. Instruction only was effective for low DFC patients, but contrary to prediction the choice was problematic for high DFC patients. It was suggested that the limited choice created reactance for these patients. The differential effectiveness of health care interventions in relation to patient predispositions was stressed.