We study how the health insurance coverage of Mexican immigrants changes with time in the U.S. Cross sectional estimates indicate that time since arrival is negatively correlated with the probability of being uninsured for both male and female Mexican immigrants, and about a third of the decline could be attributed to civic and labor market incorporation of Mexican immigrants. However, much of the relationship between time in the U.S. and health insurance coverage, after adjusting for demographic and labor market factors, is due to failure to control for age at arrival and period of arrival. Estimates from longitudinal analyses suggest that there is no systematic relationship between time in the U.S. and health insurance of Mexican immigrants, although imprecision in the fixed effects estimates makes it difficult to draw firm conclusions.