Two sesquiterpenes (1 - 2), a tetralone (3), and two phenylpropanoids (4 - 5) were isolated from the stem bark of Magnolia obovata Thunberg (Magnoliaceae) through repeated column chromatography. Their structures were identified as ${eta}-eudesmol$ (1), cryptomeridiol (2), 4R-4,8-dihydroxy-${eta}-tetralone$ (3), trans-pcoumaryl aldehyde (4), and p-coumaric acid (5) on the basis of spectroscopic analysis including two dimensional NMR and mass. Compounds 1 - 3 were tested in vitro for their cytotoxic activity against the K562, HeLa, A549, and HCT116 cancer cell lines. However, compounds 1 - 3 were inactive in this assay system.