The feasibility of using loofa (Luffa cylindrica) sponge as a carrier for the immobilization of plant cells was investigated. The immobilization capacities of suspension-cultured cells of the plant species Coffea arabica, Carthamus tinctorius and Angelica sinensis, were examined to verify the effect of aggregate size and the parts of the loofa sponge used for immobilization. C. arabica cells with large aggregate size were effectively immobilized on the loofa sponge matrix by entrapment within the random lattice network configuration. The capacity of C, arabica cells to immobilize on loofa sponge was high when tile aggregate size was above 500 mu m. Sponge segments including both the core and peripheral parts (core/peripheral part) were more efficient immobilizers than those consisting only of the core or the peripheral parts. The immobilization capacities, in a 3 d flask incubation of C. arabica cells, were 0.38, 0.32 and 0.26 g immobilized cells/g sponge for core/peripheral, core and peripheral parts of the loofa sponge, respectively. In a bubble column, a high immobilization capacity of 0.42 g immobilized cells/g sponge for C. arabica cells, after 3 d of incubation, was obtained using the core/peripheral part of the sponge. The immobilization capacity of loofa sponge was found to he comparable to that of polyurethane foam regardless of the cultivation time. It is expected that loofa sponge may he used as an excellent carrier for the immobilization of plant cells.