Compact callus aggregates (CCA) of Rhodiola sachalinensis, spherical, smooth-surfaced clumps of 2-8 mm in diameter displaying some level of tissue differentiation, were successfully cultured in 10 dm(3) and 100 dm(3) air-lift reactors. High salidroside yields of 60.0 mg dm(-3) were obtained, which were 10-fold the dispersed cell cultures. The salidroside accumulation was found to be growth-associated due to the differentiated structure of CCA. No ＇foaming＇ was observed since the broth remained almost clear throughout the culture cycle. The size of CCA conformed to normal distribution with average diameters varying from 3.1 mm to 3.6 mm during the culture. The depositing velocity of CCA in culture broth was small enough to be readily retained in suspension, therefore avoiding the clogging of the reactors. The significant increase in solid hold-up of the culture system was suggested to contribute to the variation of k(L) a during the culture.