The rapid and reproducible expansion of highly specific T cells from low precursor frequencies to clinically relevant numbers is essential for the success of autologous cell therapy techniques. The Xuri Cell Expansion System uses media perfusion and a rocking platform to achieve cell densities > 10 × 106/mL in single-use bioreactors. Achieving high cell densities in a closed environment allows for therapeutic doses to be grown in a single vessel, minimizing the risk of patient sample contamination and enabling cultures to be grown in smaller volumes, therefore saving on media expense and space requirements. The rocking motion is critical for efficient gas and media mixing and is set by changing the rocking rate and the angle at which the platform tilts. For T cells grown in a 1 L culture volume, our standard rocking conditions have been previously set at 10 rocks per minute (rpm) with an angle of 6º. We wanted to determine how these parameters individually influence the final cell density so we could determine the optimal settings for maximum cell growth.