The jury trial rights of litigants and the jury service rights of citizens are protected by the jury trial provisions of the 6th amendment and the equal protection and due process aspects of the 14th and 5th amendments. Since the 1940's, the Supreme Court has interpreted the Constitution to require that jury pools be representative of a cross-section of the community and has established extraordinarily stringent standards to guarantee representativeness. Moreover, the Federal Jury Selection and Service Act endorses a random selection process for jurors and prohibits exclusions from juries based on race, religion, sex, national origin, or economic status. Within these parameters, jury challenges can attack the adequacy of the source list, random selection procedures, the qualification process, summoning and empanelling, proportional limitations or tokenism, or grand jury issues. This paper discusses each basis for challenge and the applicable laws before addressing issues encountered in almost all challenges -- cognizable groups, proof and evaluation of underrepresentation, and the Government's rebuttal case. It identifies the following groupings as the most often raised cognizable classes: race and ancestry, socioeconomic or class status, sex, age, students, geography, education, residency requirements, religion, and political beliefs and values. Methods used to compare the composition of the community with the composition of the jury pool are surveyed, as are standards for evaluating underrepresentation. The final section considers the most frequent procedural obstacle to jury challenges, timeliness, and then examines standing and affirmative civil suits. The paper includes 123 footnotes.