Starting with the 2019 plan year, Medicare Advantage (MA) plans are able to offer expanded supplemental benefits that support their members’ broader health needs. New regulations and guidance from the Centers for Medicare & Medicaid Services (CMS) allow MA plans to offer benefits that are not traditional medical services and to target them to enrollees who would benefit most from them. Many of these new benefits are particularly valuable for members with serious illness, who have multiple chronic or debilitating conditions and face complex care needs. Despite this new flexibility, offerings of new supplemental benefits for the seriously ill have been limited in the first two years in which they were allowed. In this brief, we examine the proliferation of supplemental benefits for serious illness populations, including geographic and market trends in offerings. We also report what we learned from MA plan leaders about the challenges they face in designing and implementing new supplemental benefits.