This doctoral dissertation looks at the Iranian nuclear program, U.S. policy, and the nonproliferation regime from 1974 to 1978. By studying these three topics together, the present work sheds new light on all of them. It is argued that the primary goal of the Iranian nuclear program under Mohammad Reza Pahlavi (better known as the Shah) was nuclear energy. Transitioning away from petroleum to plutonium was part of the Shah’s plan to rapidly modernize the Iranian economy. However, the program also sought to create a nuclear weapon option, including weapons-usable fissile material, delivery vehicles, and a weapon design. Iran under the Shah sought to build the program virtually from scratch mainly through foreign assistance. Yet it found itself confronted by the United States which, after the Indian “Smiling Buddha” peaceful nuclear explosion of May 1974, sought to strengthen the nuclear nonproliferation regime and limit the diffusion of sensitive nuclear technology. Iran, by virtue of the nature and scale of its nuclear ambitions and position in the international system, became the main adversary within the nonproliferation regime of U.S. policy in the 1970s. This played out in bilateral forums, namely U.S.-Iran nuclear cooperation negotiations, and multilateral forums, like the Iran (or Persepolis) Conference on the Transfer of Nuclear Technology. This adversarial relationship culminated in the failure of the U.S.-Iran nuclear negotiations before the Iranian Revolution of 1979, in part over the discovery of covert Iranian nuclear weapons activity.