Six-month methadone-maintenance response and outcome were examined for African-American and Hispanic men and women in a large urban sample. A consistent pattern of improvement was indicated for both races and genders on the addiction severity index (ASI). There were virtually no statistically significant differences in ASI outcomes between Hispanics and African-Americans and men and women using conventional analysis of variance (ANOVA) procedures. Results from an additional equivalence analysis, however, indicated that baseline to 6-month changes for the different groups were generally not similar enough to consider them equivalent. Urine toxicologies obtained during the 6-month treatment period were also not statistically equivalent by race and gender. Evaluating outcomes by gender and race are discussed, as are the implications of using equivalence tests when examining group differences.