This booklet details the security clearance hearing of J. Robert Oppenheimer (1904-1967), a pivotal figure in the development of nuclear physics and the atomic bomb, conducted between April and May 1954. The documentation provides an overview of the hearing, including key letters, recommendations, and findings that led to the revocation of Oppenheimer's security clearance before its expiration. This decision stemmed from worries about his past affiliations and doubts over his trustworthiness despite his acknowledgement of his loyalty to the U.S.