There is a strong relation between socioeconomic position and health outcomes, although the mechanisms are poorly understood. The authors used data from 1,503 California participants in the 1998-1999 Sacramento Area Latino Study on Aging aged 60-100 years to ask whether socioeconomic position is related to immune function as measured by the body's ability to keep latent herpesvirus antibody levels in a quiescent state. Individuals with lower educational levels had significantly higher levels of immunoglobulin G antibodies to cytomegalovirus and herpes simplex virus type 1. The odds ratio for being in a higher tertile of cytomegalovirus antibodies was 1.54 (95% confidence interval: 1.18, 2.01) for those in the lowest educational group, and the odds ratio for being in a higher tertile of herpes simplex virus type 1 was 1.63 (95% confidence interval: 1.25, 2.13). The relation between education and cytomegalovirus and herpes simplex virus type 1 antibody levels remained strong after controlling for baseline health conditions, smoking status, and body mass index. This is the first study known to show a relation between socioeconomic position and immune response to latent infection. It provides suggestive evidence that modulation of the immune system via latent infections may play a role in the observed associations between socioeconomic position and disease.