We study racial/ethnic disparities in awareness of chronic diseases using biomarker data from the 2006 Health and Retirement Study. We explore two alternative definitions of awareness and estimate a trivariate probit model with selection, which accounts for common, unmeasured factors underlying the following: (1) self-reporting chronic disease; (2) participating in biomarker collection; and (3) having disease, conditional on participating in biomarker collection. Our findings suggest that current estimates of racial/ethnic disparities in chronic disease are sensitive to selection, and also to the definition of disease awareness used. We find that African-Americans are less likely to be unaware of having hypertension than non-Latino whites, but the magnitude of this effect falls appreciably after we account for selection. Accounting for selection, we find that African-Americans and Latinos are more likely to be unaware of having diabetes compared to non-Latino whites. These findings are based on a widely used definition of awareness – the likelihood of self-reporting disease among those who have disease. When we use an alternative definition of awareness, which considers an individual to be unaware if he or she actually has the disease conditional on self-reporting not having it, we find higher levels of unawareness among racial/ethnic minorities versus non-Latino whites for both hypertension and diabetes. Copyright © 2012 John Wiley & Sons, Ltd.