Here we describe a simplified method for transient gene expression (TGE) in suspension-adapted Chinese hamster ovary (CHO) cells using polyethylenimine (PEI) for DNA delivery. Both the transfection and production phases of the bioprocess were performed at a density of 4×106cells/mL at 31°C. In addition, the amounts of both PEI and plasmid DNA were reduced up to 50% on a per cell basis compared to previously published protocols from this laboratory, resulting in higher cell viability after transfection and higher volumetric recombinant protein yields. In batch cultures of up to 14days, reproducible recombinant antibody yields up to 300mg/L were achieved at small scale (5mL) and up to 250mg/L at large scale (500mL). The simplicity and improved yields are expected to increase the utility of CHO cells for the rapid production of recombinant proteins at larger scales by TGE.