Spodoptera frugiperda (Sf9) insect cells were successfully cultured in serum-free medium in a 14-L airlift bioreactor. Cell densities as high as 1 × 107 cells/mL were achieved with specific growth rates of approximately 0.0286 h−1 (doubling time of 24 h). This system was also used to demonstrate the expression of a reported gene, β-galactosidase (β-gal), when cells were infected with a recombinant baculovirus. Approximately 0.33 mg of β-gal/mL (i.e., 104 000 units/mL) of medium were obtained at the 14-L scale, while about 0.95 mg of β-gal/mL (i.e., 285 000 units/mL) of medium were obtained in small-scale shaker flasks. The difference was attributed to a suboptimal infection in the large scale. Specific oxygen consumption rates decreased from 5.58 × 10−17 mol O2cell·s in early exponential growth to 3.13 × 10−17 mol (O2cell·s at 3 days post-infection.