Federal standards established in 1997 allow respondents to select multiple-race categories. These new standards changed the single-race subgroup definitions that the government has required since 1977. Meta-analysis, research on long-term assessment trends, and other research involving historical comparisons must account for the definitional changes. Researchers have proposed bridging methods as techniques for linking the old and new definitions. The authors describe covariate and noncovariate bridging methods and evaluate their efficacy. The authors conceptualized covariate procedures as finite mixture models that researchers may use in either single or multiple imputation. A simulation study of single-imputation bridging indicated that the use of covariates notably improves the efficacy of bridging. (Contains 10 tables, 2 figures, and 3 notes.)