A K1 subclone of a parental Chinese hamster ovary (CHO) cell line has been optimized for protein production. The cell line has been adapted to grow under suspension and adherent cultured conditions. Cell growth has been further adapted to expand under serum-free conditions using our companion CHO media. The CHO cell morphology is depicted under phase microscopy (Figure 1). An example of protein production is illustrated by the expression of a green fluorescent protein (Figure 2).