In a chemical study of antiproliferative related Umbelliferae plants of Yunnan Province, China, eight compounds, including two new coumarins, lidaucoidins A and B (1,2), were isolated from the roots of Ligusticum daucoides Franch. The identification and structural elucidation of the new isolates were based on spectral data analysis including extensive 1D and 2D NMR. All coumarins obtained were assayed for their cytotoxic ability against SW480, human tumor cell lines.The use of Umbelliferae in Chinese popular folk medicine has a long tradition. During research on the active components of the Chinese crude drug "Qian-Hu" belonging to Umbelliferae, Sun et al. phytochemically investigated 14 "Qian-Hu" species distributed in the southwest of China that have important bioactivities, structural complexity, and interesting chemical diversity of composition. Forty-six coumarins have been isolated and characterized, comprising simple coumarin, linear furocoumarin, angle furocoumarin and angle pyranocoumarin types. Most importantly, these related analogous isolated coumarins have been found to have antiproliferative, anti-inflammatory, acetylcholinesterase inhibitory, and antiplatelet activities [1][2][3][4]. "Han Qian-Hu," the roots of Ligusticum daucoides Franch., an important perennial herb widely found in the Yunnan Province of China, have been used in the treatment of rheumatic disease in folk medicine. Previous phytochemical investigation of this herb resulted in four coumarins, anomalin, pteryxin, osthol, and nodakenin [1]. In our continuing research program with the aim of discovering new coumarins with diverse structures and bioactivities, we have reinvestigated the roots of L. daucoides Franch. collected in Dali, Yunnan Province and isolated eight compounds, including two new coumarins, lidaucoidins A-B (1, 2), along with six known compounds, vaginidiol (3) [5], vaginol (4) [6], hyuganin E (5) [7], oxypeucedaninhydrate (6) [8], ferulic acid (7) [9], and E-sitosterol (8) [10]. In this paper, we present the isolation, structure elucidation, and cytotoxicity of two new and known coumarins.