Not enough is known about the prevalence of housing discrimination against persons with disabilities. Only slightly more than half of Americans know that it is illegal for landlords to refuse to make reasonable accommodation for persons with disabilities or to permit reasonable modification to a housing unit. The U.S. Department of Housing and Urban Development (HUD) contracted with the Urban Institute to advance the state of the art in testing to measure discrimination against persons with disabilities. UI found that persons with the disabilities studied encountered significant levels of adverse treatment when searching for rental housing in the Chicago area--even more than that of African-American or Hispanic renters in the Chicago-area housing market.