Medicinal plants are the most promising source for the development of drugs, and many types of active ingredients from the plant resources have been studied in order to clarify the relationship between the chemical structure and the activity. However, it is not easy to develop drugs from those active compounds, and in many cases, the supply of active compounds can have some problems: 1) limited quantity of active compounds in plant; 2) low plant growth rate; 3) the limited localization of active ingredients in the specific organs; and 4) from the perspective of the conservation of natural resources. Therefore, the stable supply of the compounds commercially is very difficult and contains risk hedge. Plant cell culture is an attractive technology to solve these problems by securing the stable supply of the active compounds without damage to the natural plant resources. Recently, an efficient production process of anticancer drug paclitaxel by Taxus cell suspension cultures was constructed. The established Taxus cell lines produced paclitaxel and related taxanes by specific external stimuli, such as methyl jasmonate. The time-course analysis revealed that there are two regulatory steps existing in the paclitaxel biosynthesis: the taxane-ring formation step that is up-regulated by MeJA, and the acylation step at the C-13 position. By applying the data from the two-stage culture and the high-density culture, a large-scale culture process was developed with a stable paclitaxel production in the range of 140-295 mg L-1, reaching 295mg L-1 at maximum.