The paper describes different concepts of bias in tests and presents data on the possible effects of using sociocultural background in the interpretation of standardized test results. Five different definitions of the concept of test bias are explored: equality of means among groups, equal proportions, fairness in predictions, social utility model, and construct validity bias. Assessment data on 1040 children from four ethnic-racial groups (in grades 1, 3, 5, 7, and 9) using conventional and system of multicultural Pluralistic Assessment measures is considered in terms of the above definitions. Among conclusions is that conceptions of test bias are extremely complex and diverse. Tables with statistical data are provided. (SBH)