UCLA research finds that a refundable State-level Earned Income Tax Credit (SEITC) of 10% or above the Federal EITC was associated with a 21% relative risk reduction in reported behavior that could put single mothers at high risk for becoming infected with HIV during the previous year. Also, a 10 percentage-point increase in SEITC was linked to a 38% relative reduction in the same reported high-risk behavior the previous year.