Arguably among the biggest tasks facing the health insurance marketplaces established by the Affordable Care Act (ACA) has been the creation of an information technology (IT) system (including a self-service enrollment web site) that determines eligibility for and facilitates enrollment into health coverage. This paper examines the development and performance of ACA-compliant eligibility and enrollment systems for health insurance marketplaces in eight states. Some of these states IT systems are operating smoothly while others have struggled to overcome technical glitches for months. These early successes and stumbles are reflected in marketplace-based enrollment numbers during the ACAs first months of open enrollment.