In this paper, I examine the impact of uninsured patients on the health of the
insured, focusing on one health outcome | the in-hospital mortality rate of insured
heart attack patients. I employ panel data models using patient discharge and hospital
nancial data from California (1999{2006). My results indicate that uninsured patients
have an economically signi cant e ect that increases the mortality rate of insured heart
attack patients. The primary channel for the observed spillover e ects is increased
hospital uncompensated care costs. Hospitals, in return, provide a greater quantity of
cardiac services with less cardiac care staff.