Many policy makers believe that health status would be improved and health care spending reduced if people managed their health better. This study examined the effectiveness of a program put in place by BJC HealthCare, a hospital system based in St. Louis, Missouri, that tied employees' eligibility to participate in the system's most generous health plan with participation in a wellness program. The intervention, which began in 2005, was associated with a 41 percent decrease, relative to a comparison group, in hospitalizations for conditions targeted by the wellness program but with no significant decrease in other hospitalizations. We found reductions in inpatient costs but similar increases in non-inpatient costs. Therefore, we conclude that although the program did cut some hospitalizations, it did not save money for the employer in the short term. This finding underscores that wellness program incentives under the Affordable Care Act are unlikely to greatly reduce health care spending over the short run.