The effects of the three polyacetylene compounds, panaxynol, panaxydol and panaxytriol, on in vitro-cell growth were studied. These compounds are much different in their water-solubility. In order to increase water-solubility, solid complexes of polyacetylene compounds with alpha-cyclodextrin (CD) were prepared. Accurate concentrations of the active compounds in a culture medium were determined by gas chromatography. All of these CD-complexes inhibited the growth of various kinds of cultured cell lines in a dose-dependent fashion. The cell growth inhibitory activity of these complexes was much stronger against malignant cells than against normal cells. A continuous contact between the compounds and target cells was not necessarily required for growth inhibition. And the inhibition was cytotoxic at high concentrations and cytostatic at low concentrations. These findings indicate that these polyacetylene compounds' mode of action is more dose-dependent than time-dependent. The panaxynol, panaxydol and panaxytriol contents in red ginseng powder were 250, 297 and 320 micrograms/g, respectively.