Chinese hamster ovary (CHO) cells are widely used to produce recombinant proteins as therapeutics for a variety of diseases. These proteins often contain carbohydrates that are critical for therapeutic efficacy. Now Krummen and colleagues have engineered CHO cells that overexpress two enzymes responsible for adding N-linked oligosaccharides. Therapeutic IgGs produced in these cells had more complete carbohydrate modifications and persisted longer in an animal model system (see p. 1116).