The effects of various elicitors, metabolic inhibitors and growth regulators on the production of diterpenoid anticancer agent taxol were investigated in cell suspension cultures of Taxus brevifolia. Cell cultures of T. brevifolia were treated by 5 kinds of biotic elicitors, 5 kinds of abiotic elicitors, 2 kinds of metabolic inhibitors and 8 kinds of growth regulators at the end of exponential growth phase. Among those treatments, chlorocholine chloride-an inhibitor of plant steroid metabolism-increased the taxol production most significantly. From a series of optimization studies, it was found that the addition of 1mM of chlorocholine chloride at the 9th day of culture was the best for taxol production. Taxol yield under this condition was 0.72mg/$ell$.