Legislative restrictions in immigrants' access to health care and local governmental funding shortfalls in the US and Western Europe have raised fears that public clinic patients might delay care for communicable diseases. To help quantify the potential impact of both policies on public clinics providing sexually transmitted disease (STD) services, we surveyed 234 patients from five LA clinics regarding their alternative sources of health care. Of the 215 providing complete information (response rate = 91%), 52 (24%) reported they had no legal rights to reside in the US. Compared to the legal resident control group, illegal immigrants were more likely to indicate that they had no alternative access to medical care (27% vs 44%; P = 0.03). We conclude that for a substantial proportion of patients, particularly illegal immigrants, the STD clinics are indeed essential. Restricting access to these clinics may have unpredictable public health consequences.