Resumo. The main objective of this work is to study the index forest sites build, for the dominant height, of populations located in the central area of the state of Rio Grande do Sul. To do that, information from 3 stands located at FEPAGRO was used. To construct the curves index sites forest, information from 18 dominant trees was collected in the 4 sites, observing the methodology for the analysis of the bole. For the curves index site forest, the Backman model was, and it was verified the necessity of construction of two groups of index curves of sites, with space of 2 m, from 4 to 25 years, and index age of 25. To the site IA, 3 index curves were generated, from 22 to 24 m and, to the sites I-B+II+III, 6 index curves from 8 to 18 m were made.