Past and present, those with the greatest healthcare needs often receive the least adequate healthcare. This phenomenon, termed the "inverse care law," has implications for healthcare and outcomes for vulnerable populations including low-income persons, racial and ethnic minorities, and the uninsured among others. This article reviews disparities in health status and access to healthcare for vulnerable populations. It illustrates how concentration of risk factors within individuals, families, and communities worsens the paradox between healthcare need and access and highlights the models of healthcare delivery needed to adequately meet the needs of vulnerable populations.