A dichloromethane extract of root celery yielded falcarinol, falcarindiol, panaxydiol, and the new polyacetylene 8-O-methylfalcarindiol. The structure of the new compound was established by one- and two-dimensional (1D and 2D) NMR, mass spectrometry, and optical rotation data. Nonpolar extracts of roots and bulbs of carrots, celery, fennel, parsley, and parsnip were investigated for their content of polyacetylenes by high-performance liquid chromatography with diode array detection (HPLC-DAD). All five species contained polyacetylenes, although carrots and fennel only in minor amounts. Additionally, the cytotoxicity of the four polyacetylenes against five different cell lines was evaluated by the annexin V-PI assay. Falcarinol proved to be the most active compound with a pronounced toxicity against acute lymphoblastic leukemia cell line CEM-C7H2, with an IC(50) of 3.5 micromol/L. The possible chemopreventive impact of the presented findings is discussed briefly.