Palavras-chave: Ocimum basilicum, substrato comercial, número de células.ABSTRACT: Development of basil seedlings(Ocimum basilicum L.)in different density and type of substrates and trays. One of the most important stages in the production of basil is the development of seedlings. In this step, care with the container and the substrate is essential, because it directly affects the root growth and architecture, as well as the supply of nutrients. Thus, the objective of this study was to evaluate the development of basil seedlings (Ocimum basilicum L.) influenced by the type and density of different substrates, grown in polystyrene trays with different cell numbers. The experiment was conducted at the Gardening area of the Federal University of Grande Dourados (UFGD) inDourados-MS, Brazil.