Improvements in single-use systems have allowed implementation of high-density cultures in standard workflows. This study shows the integration of the Thermo Scientific™ HyPerforma™ Single-Use Bioreactor (S.U.B.) and the Repligen XCell ATF™ 6 Single-Use System to achieve a stable, high-density perfusion cell culture, at 40 x 106 cells/mL over 20 days, without modifying the standard systems. The data show that an integrated HyPerforma S.U.B. and XCell ATF 6 system can be used in a high-density seed train or as a production vessel system.