A new cyanoglucoside, purshianin (1), was isolated together with a known cyanoglucoside, menisdaurin (2a), from stems of Purshia tridentata DC. (Rosaceae) collected in Oregon, U.S.A. and the structure was established as (4S, 6S)-(Z)-6-(β-D-glucopyranosyloxy)-4-hydroxy-2-cyclohexene-Δ^{1, α}-acetonitrile (1) based on chemical and spectral evidence. Notably, the absolute structure of 1 and the revised stereostructure (2), (4S, 6R)-(Z)-6-(β-D-glucopyranosyloxy)-4-hydroxy-2-cyclohexene-Δ^{1, α}-acetonitrile for menisdaurin were decided based on combined studies of difference NOE spectra and Dreiding model inspection.