Although chronically ill individuals need protection against high medical expenses, they often have difficulty obtaining adequate insurance coverage due to medical underwriting practices used to classify and price risks and to define and limit coverage for individuals and groups. Using data from healthy and chronically ill individuals in Indiana, we found that illness decreased the probability of having adequate insurance, particularly among single individuals. Chronic illness decreased the probability of having adequate coverage by about 10 percentage points among all individuals and by about 25 percentage points among single individuals. Pre-existing condition exclusions were a major source of inadequate insurance. Our results emphasize the impact of enforcing the Health Insurance Portability and Accountability Act (HIPAA) of 1997, which limits pre-existing condition exclusions.