Mass-production of regenerated plantlets using alginate bead encapsulating carrot callus was studied. When gel beads were cultivated in a flask containing regeneration medium, somatic embryos were released at high frequency from the gel beads and developed into plantlets, When a callus less than 320 mu m in size was immobilized in the beads, a larger number of embryo was released from the beads. At 0.11 ml-pcv/ml-gel of inoculum size, the maximum number of embryo was obtained. In order to develop a suitable bioreactor for the immobilized callus system, three types of bioreactors, namely air-lift, horizontally shaking vessel and rotating mesh-basket types, were tested. In the case of the rotating mesh-basket type, a larger amount of released cells was obtained. Plantlet formation from the released cells reached a level of 115% compared with that of the flask culture. To achieve continuous recovery of released cells and perform long term culture, a cyclone type cell separator was designed and used in conjunction with a rotating mesh-basket type bioreactor, When 110 ml/min of medium flow was passed through the separator, 90% of suspended cells were collected after 40 min of operation time. Long term cultures at 50, 100, and 150 rpm of rotational speed were carried out. In the experiment at 100 rpm, almost constant values of released cell volume and number of embryos were obtained during 12 d. They were 3 ml-pcv/l-medium/d and 7000 plantlets/g-released cells, respectively.