Abstract: For the production of taxol (paclitaxel) by immobilized cells cultured in a bioreactor, cells prepared from Taxus cuspidata var. nana were entrapped with calcium alginate and the amount of paclitaxel released into F4G4 liquid medium was investigated. Immobilized cell cultures were developed using various calcium alginate gel concentrations (2, 2.5 and 4% w/v) and cell concentrations (3, 5 and 10% w/v). Some of the paclitaxel produced in the immobilized cells was found to be released into F4G4 liquid medium. The amount released depended on the gel and cell concentrations used. The free cells in suspension cultures accumulated paclitaxel in intracellular compartments, while the cells immobilized with the calcium alginate gel released some paclitaxel into the medium. The gel forced some of the paclitaxel produced in the cells to be released into the medium. When the cultures using immobilized cells entrapped at a 3% cell concentration and 2.5% gel concentration with an air-lift bioreactor were conducted for 30 days, the amount of paclitaxel released into the medium increased with time on the addition of an elicitor, chito-heptaose. The release of paclitaxel was enhanced to 2.4 mg L-1 of culture medium after the 30-day-incubation. This is the first report that the release of paclitaxel into the medium by immobilized cell cultures of Taxus sp. was enhanced by the addition of an elicitor. Eight five percent of the paclitaxel produced in the cells was released by the immobilized cell cultures in 30 days. The results obtained in this study, with immobilized T. cuspidata var. nana cells in a 2.5% calcium alginate gel, may pave the way for the production of paclitaxel by immobilized cell cultures in a bioreactor.