Recent changes to federal guidelines for the collection of data on race and ethnicity allow respondents to select multiple race categories. Redefining race subgroups in this manner poses problems for research spanning both sets of definitions. NAEP long-term trends have used the single-race subgroup definitions for over thirty years. Little is known about the effects of redefining race subgroups on these trends. Bridging methods for reconciling the single and multiple race definitions have been developed. These methods treat single-race subgroup membership as unknown or missing. A simulation study was conducted to determine the effectiveness of four bridging methods: multiple imputation logistic regression, multiple imputation probabilistic whole assignment, deterministic whole assignment--smallest group, and deterministic whole assignment--largest group. Only the first of these methods incorporates covariate information about examinees into the bridging procedure. The other three methods only use information contained in the race item response. The simulation took into account the percentage of biracial examinees and the missing data mechanism. Results indicated that the multiple imputation logistic regression was often the best performing method. Given that all K-12 and higher education institutions will be required to use the multiple-race definitions by 2009, implications for No Child Left Behind and other federally mandated reporting are discussed.