This chapter provides an analysis of seniority rights under Title VII of the Civil Rights Act of 1964, which bars discrimination in employment. Two legal theories have arisen in assessing Title VII claims: discriminatory treatment, in which the burden of proof of discriminatory intent lies with the plaintiff, and discriminatory impact of neutral practices, in which the burden shifts to the employer to prove that the practice in question is a legitimate business necessity. Because Title VI insulates seniority systems from disparate impact suits, Title VII litigation focuses on what constitutes a bona fide seniority system and scope of immunity. The question addressed in the ensuing discussion is therefore as follows: under what circumstances must seniority adjustments be made, and how much discretion do employers have in modifying operation of seniority systems to give preference to women and minorities? Cases in which the judiciary has addressed these and related Title VII issues are analyzed under the following headings: (1) retroactive seniority (for employees previously denied employment in the same firm for discriminatory reasons); (2) bona fide status (covering legal definitions of bona fide seniority systems); and (3) affirmative action plans (to remedy the adverse effects of seniority systems on victims of prior discriminatory employment practices). The concluding section alludes to counterclaims of reverse discrimination arising from modification of seniority systems to give preference to women and minorities. (TE)