A high reproducibility of batch growth of Catharanthus roseus could only be achieved by using identical inoculum material. It was found that the initial growth rate of the cells increased with increasing inoculation density, whereas the maximum growth rate was not affected. Withdrawal of the conditioned medium from the inoculum resulted in a strong decline in the initial growth rate, indicating that conditioning factors affected the initial growth rate. Neither increasing the air flow rate from 0.5 to 1.5 volume of air per volume of broth min(-1) (vvm) nor CO2 enrichment of the aeration gas had any effect on the growth of the cells.