Productivity of three different promoters at various cell cycle stages and under two distinct growth conditions was examined in Chinese hamster ovary cells. Under the Growth Arrest and DNA Damage inducible GADD153 promoter, productivity of the short half-live variant of the enhanced green fluorescent protein (d2EGFP) and the secreted alkaline phosphatase (SEAP) was highest at the G1 phase of the cell cycle and at serum starvation, while under the cytomegalovirus (CMV) or the simian virus SV40 promoter, productivity was highest at S-phase and in complete medium. These results indicate the utility of the GADD153 promoter for production purposes under protein-free conditions.