The 2005 federal Deficit Reduction Act made proof of citizenship a requirement for Medicaid eligibility. We examined the effects on visits to Oregon's Medicaid family planning services eighteen months after the citizenship requirement was implemented. We analyzed 425,381 records of visits that occurred between May 2005 and April 2008 and found that, compared to the eighteen-month period before the mandate went into effect, visits declined by 33 percent. We conclude that Medicaid citizenship documentation requirements have been burdensome for Oregon Family Planning Expansion Project patients and costly for health care providers, reducing access to family planning and preventive measures and increasing the strain on the safety net.