BACKGROUND: National and state surveys show large disparities in pneumococcal vaccination status among Whites, Blacks and Latinos aged >/= 65. The purpose of this study is to determine whether there is any difference in the validity of self-report for pneumococcal vaccination by race/ethnicity that might contribute to the substantial disparities observed in population-level coverage estimates. METHODS: Self-reported vaccination status was compared with medical record documentation for samples of White, Black, and Latino members of a large health plan to examine whether differences in validity of self-report contribute to observed disparities. RESULTS: Sensitivity was significantly lower for Blacks (0.849, 95% CI 0.818-0.876) and Latinos (0.869, 95% CI 0.847-0.889) than for Whites (0.931 95% CI 0.918-0.942). Specificity was somewhat higher for Blacks than for Latinos and Whites, but the differences were not statistically significant. Coverage for Whites, Blacks and Latinos, respectively, was 84.3%, 73.5%, and 82.3% based on self-report, but 74.8%, 71.9%, and 84.2% based on medical records. CONCLUSION: The results of this study suggest that differential self-report error, i.e., summative effect of over-reporting and under-reporting within a race-ethnic group, may contribute to the size and direction of race-ethnic disparities in pneumococcal vaccination observed in surveys.