An Australian Babesia bigemina vaccine strain was maintained in suspension culture for 40 days. Parasite growth was compared using two tissue-culture flask sizes (25 and 75 cm2), four gas mixes (2%, 2.5%, 3% and 3.5% O2; 5% CO2; and the balance N2) and four packed blood cell (PCV) volumes (7%, 9%, 13% and 18%). The best continuous parasite yields were obtained from suspension cultures in 75-cm2 flasks at a PCV of 13% and gas mixtures of 2%-3% O2, 5% CO2 and the balance N2. Parasite yields per millilitre of culture medium were 3 times those obtained in microaerophilous stationary-phase cultures. The method has thus far been used for 6 months to produce the Australian requirements for live B. bigemina vaccine.