Two new abietane-type diterpenes, 3beta-hydroxy-9alpha, 13alpha-epidioxyabiet-8(14)-ene (1) and 3-oxo-9alpha,13alpha-epidioxyabiet-8(14)-ene (2), were isolated from the methanolic crude extract of the petioles of Sagittaria montevidensis ssp montevidensis (Alismataceae). The structures of 1 and 2 were determined on the basis of spectrometric analyses including HREIMS, IR as well as ¹H and 13C 1 and 2D NMR.Dois novos diterpenos do tipo abietano 3beta-hidroxi-9alfa, 13alfa-epidioxiabiet-8(14)-eno (1) e 3-oxo-9alfa,13alfa-epidioxiabiet-8(14)-eno (2) foram isolados do extrato bruto metanólico dos pecíolos de Sagittaria montevidensis ssp montevidensis (Alismataceae). As estruturas de 1 e 2 foram determinadas com base em análises espectrométricas do tipo EM-AR, IV, bem como, RMN de ¹H e 13C uni e bi dimensionais.444447