This article analyzes the difficulties imposed on researchers of prison institutions. The starting point was the experience in the development of empirical research in Women’s Penitentiary Madre Pelletier and Presidio Central de Porto Alegre, between 2013 to 2015. We reflect on the entry field and barriers found to carry out the research, which will beyond the initial authorization to its beginning. Besides the bureaucratic difficulty getting approval from regulators and ethics committees, researchers face obstacles imposed by the relations established with the observed individuals. In addition, researchers are perceived in different ways: as an enemy of legal operators and professionals who occupy the space of the prison and criminal justice; as someone whose work involves more work and as one that records stories and life experiences, information. The entry in the field, therefore, means the need to conquer space, establish relationships with people and power. Therefore, research in prison under shown complex and difficult, but necessary to understand a diverse and paradoxical place.