Recombinant human cyclooxygenase 2 (Cox 2) was expressed in stably transformed Drosophila melanogaster S2 cells, and was present primarily in the cellular fraction at a molecular weight of 70 to 74 kDa. Recombinant Cox 2 was purified using Ni2+-affinity fractionation to a specific activity of 24 800 U mg(-1) protein. The peak level of recombinant Cox 2 production was 1.6 mug (10(7) cells)(-1), seven days after induction with 0.5 mM CuSO4. Supplementing the cultures with dimethylsulfoxide or sodium butyrate increased recombinant Cox 2 production by 170% and 86%, respectively.