Every year, an estimated 33.5 million people experience a life-changing event that ends health coverage while making them eligible to enroll in marketplace plans outside standard open enrollment periods. By far the most frequent trigger for such special enrollment periods (SEPs) is job loss that ends employer-sponsored insurance. The second-most common SEP involves consumers whose increased income terminates Medicaid eligibility. Based on data through June 2015, fewer than 15 percent of the uninsured who qualify for SEPs will use them to enroll in marketplace plans. Application assistance campaigns focusing specifically on life events that commonly trigger SEPs could help both uninsured consumers and marketplaces.