Objectives. This study examined the impact of the Great Recession of 2007-2009 on public health insurance enrollment and expenditures in Alabama. Our analysis was designed to provide a framework for other states to conduct similar analyses to better understand the relationship between macroeconomic conditions and public health insurance costs. Methods. We analyzed enrollment and claims data from Medicaid and the Children’s Health Insurance Program (CHIP) in Alabama from 1999 through 2011. We examined the relationship between county-level unemployment rates and enrollment in Medicaid and CHIP, as well as total county-level expenditures in the two programs. We used linear regressions with county fixed effects to estimate the impact of unemployment changes on enrollment and expenditures after controlling for population and programmatic changes in eligibility and cost sharing. Results. A one-percentage-point increase in a county’s unemployment rate was associated with a 4.3% increase in Medicaid enrollment, a 0.9% increase in CHIP enrollment, and an overall increase in public health insurance enrollment of 3.7%. Each percentage-point increase in unemployment was associated with a 6.2% increase in total public health insurance expenditures on children, with Medicaid spending rising by 7.5% and CHIP spending rising by 1.8%. In response to the 6.4 percentage-point increase in the state’s unemployment rate during the Great Recession, combined enrollment of children in Alabama’s public health insurance programs increased by 24% and total expenditures rose by 40%. Conclusion. Recessions have a substantial impact on the number of children enrolled in CHIP and Medicaid, and a disproportionate impact on program spending. Programs should be aware of the likely magnitudes of the effects in their budget planning.