The enactment of the Affordable Care Act in 2010 led to a sharp increase in employers self-funding their group health insurance plans, with the market tripling in size in the decade that followed. While larger employers can self-fund their group medical coverage in a relatively efficient manner, it does not work well for smaller employers. As year-over-year spending on healthcare in the United States outpaces growth in real gross domestic product by wide margins, employers of all sizes continue to seek to make group health insurance coverage available to their employees at a reasonable cost. Group captive-funded medical stop-loss insurance offers a way for smaller employers to obtain the full benefit of self-funding. This Special Report explains what group medical stop-loss captives are and how they are structured and regulated.