Choosing Wisely was launched by the American Board of Internal Medicine in April 2012 as a patient- and clinician-targeted campaign to reduce potentially unnecessary "low-value" medical services. The campaign's impact on low- and high-value care beyond its first year is unknown; furthermore, it is unknown whether some patients such as members of consumer-directed health plans and people residing in different US regions have responded more than others. To evaluate the impact of Choosing Wisely, we used commercial insurance claims to track changes in the use of low-value imaging (x-ray, computed tomography, and magnetic resonance imaging) for back pain before and after the campaign began, a period running from 2010 to 2014. We selected back pain imaging because it is a prominent target of Choosing Wisely, which considers it low value except in a minority of cases, because of its relatively high out-of-pocket expense, and the large volume of low back pain visits nationally. We found only a 4 percent relative reduction in low-value back imaging 2.5 years after the start of the campaign and some differences in regional trends, but no differences associated with enrollment in consumer-directed health plans. Our findings highlight the ongoing challenge of reducing unnecessary medical care, even when patients have "skin in the game" under consumer-directed health plans.