The effects of ethylene biosynthesis inhibitors including alpha-amino isobutyric acid, CoCl2 and NiCl2, and an inhibitor of ethylene action, Ag+, on fungal elicitor-induced paclitaxel production were assessed in cell suspension cultures of Taxus chinensis, T chinensis var. mairei and T. yunnanensis to elucidate the role of ethylene in paclitaxel synthesis. All these ethylene inhibitors enhanced the paclitaxel yield, and most significantly (up to three-fold) by the combination of CoCl2 (20 muM) and Ag+ (30 muM). On the contrary, ethrel, an ethylene-releasing reagent, and acetylsalicylic acid (ASA), an inhibitor of both jasmonic acid (JA) and ethylene biosynthesis, depressed the elicitor-induced paclitaxel production. Importantly, the positive or negative effects of these ethylene inhibitors or generator on paclitaxel production were mainly observed when they were added to the culture before or simultaneously with the fungal elicitor, but became less significant or negligible when they were added 24 h after the elicitor. These findings suggest that the control of ethylene production is important for the elicitation of paclitaxel biosynthesis of the cultured Taxus spp. cells. Therefore, the application of ethylene inhibitors to Taxus cell cultures before elicitor treatment is an effective measure to enhance elicitor-induced paclitaxel production.