Phlebiopsis gigantea fungus used in biological control of root rot is currently cultivated commercially in disposable, sterilizable plastic bags. A novel packed bed bioreactor was designed for cultivating P. gigantea and compared to the plastic bag method and to a tray bioreactor. The spore viability of 5.4 x 10(6) c.f.u./g obtained with the packed bed bioreactor was of the same order of magnitude as the viabilities obtained with the other cultivation methods. Furthermore, the packed bed bioreactor was less time and space consuming and easier to operate than the tray bioreactor.