The emergence of transgenic soybean caused a negative externality for conventional farmers since recognition and certification as transgenic-free implied on high costs to make the segregation along the steps of process of production. Even though there is the possibility of contamination and losses for nontransgenic farmers, regulations of coexistence for those products practically do not exist. Consequently, this study aims to investigate the legal parameters that should exist in the Brazilian legislation to regulate the matter. This is an exploratory-descriptive research, in that data collection was conducted with agents who represent segments of the soybean Agroindustrial System. For this, semi-structured interview scripts composed by open and dichotomic questions were used. The analysis of the content verbalized by participants was made by the software Alceste and, afterwards, through manual analysis of the content, it was possible to validate the electronic examination. Some categories of analysis emerged from the speech of participants and results were organized and interpreted under the referential framework of the theory of New Institutional Economics, indicating the need of regulating specific parameters in order to assure the coexistence of both transgenic and conventional soybean.