A new cytotoxic acetogenin, chamuvarinin (1), containing a tetrahydropyran ring with an adjacent bis-tetrahydrofuran ring, which corresponds to a novel carbon skeleton in this series, was isolated from the roots of Uvaria chamae, together with the previously reported acetogenins squamocin (2), desacetyluvaricin (3), and neoannonin (4). The structure determination of chamuvarinin (1) was based on extensive NMR studies and high-resolution mass spectral measurements. This new compound shows significant cytotoxicity toward the KB 3-1 cell line (IC50 = 8 x 10(-10) M). In addition, a biosynthetic relationship between 1 and 2 is briefly discussed.