Effects of polyol lipids, 3,5-dihydroxydecanoyl and 5-hydroxy-2-decenoyl esters of arabitol and mannitol, which were produced by Aureobasidium sp., on cells of the human lung cancer cell line A549 were examined. Polyol lipids inhibited the growth of A549 cells and caused a significant decrease in the activity of the intracellular phospholipid-and Ca2+-dependent protein kinase (protein kinase C). Furthermore, polyol lipids caused an increase in the number of cells in the G0-G1 phase. The effective concentration of polyol lipids was not toxic to the growth of cells of the human diploid cell line TIG1. The polyol fraction (a mixture of arabitol and mannitol), was not effective on growth inhibition of cells but the fatty acid fraction (a mixture of dihydroxydecanoyl and hydroxydecenoyl) partially inhibited the growth of A549 cells. The result of the measurement of surface tension activity showed that the critical micelle concentration (CMC) of polyol lipids was around 10 mu g/ml, and the concentrations effective on A549 cells were above the CMC.