Resumo. The present work aimed to study the natural stand of Araucaria angustifolia (Bertol.) Kuntze growth in diameter in function of the age, in Medium Plateau, Leans Superior of the Northeast and Mountain of the Southeast phytogeographics areas of Rio Grande do Sul. For this, the Backman's growth equation had been used, showing to be efficient with application of dummy variables, allowing identifying differences in growth for the studied areas, having the need of separating equations to each place, what allowed minimizing the estimates errors. The obtained results demonstrate that in each area the species presented form and differentiated diametric growth. In the Southeast Mountain, the average annual increment in diameter had been 0,96 cm/year at 33 years; in the Medium Plateau, 0,95 cm/year at 22 years; and in the Northeast Superior Hillside, 1,04 cm/year at 20 years-old, indicating a good potential of medium growth.