In the early years of the atomic era, several developing countries attempted to establish a nuclear programme, yet Brazil's case is less well-known. As new documents show, from 1951 Brazil aimed to acquire the nuclear fuel cycle capability in spite of legislation imposed by the United States to limit the emergence of new nuclear powers. This article will analyse the origins of the Brazilian nuclear programme from 1951 to 1955 and will explore its cooperation in the atomic field with international partners.