A method for producing an ultra-high density frozen cell bank directly from a population of cultured cells, the method comprising: a) culturing cells in a perfusion bioreactor to obtain an ultra-high density cell population with a concentration of at least about 1.0 x 10 8 cells/mL, wherein said perfusion bioreactor is coupled to a cell retention system comprising an alternating tangential flow filtration system comprising a filter, wherein the perfusion bioreactor cell culture has a dissolved oxygen concentration of at least about 30%, and wherein the DO in the perfusion bioreactor is controlled through adjustment of the rock rate and rock angle of the bioreactor, wherein the bioreactor is initially rocked at 22 rpm with a rock angle of 10° and subsequently rocked at 25 rpm with a rock angle of 12°, and by manually supplying pure oxygen to the headspace when the DO is > 30%, wherein a total gas flow rate is initially 0.2 liters per minute and increased to 0.4 1pm when the cell concentration is ≥ 3 x 10 7 cells/mL or > 4 x 10 7 cells/mL; and b) adding cryoprotectant to the ultra-high density cell population to produce an ultra-high density frozen cell bank, wherein the ultra-high density frozen cell bank has a concentration of at least about 1.0 x 10 8 cells/mL and a post-thaw viability of at least about 95%, and wherein no additional concentrating step is performed between culturing the cells and adding cryoprotectant to the ultra-high density cell population. a) culturing cells in a perfusion bioreactor to obtain an ultra-high density cell population with a concentration of at least about 1.0 x 10 8 cells/mL, wherein said perfusion bioreactor is coupled to a cell retention system comprising an alternating tangential flow filtration system comprising a filter, wherein the perfusion bioreactor cell culture has a dissolved oxygen concentration of at least about 30%, and wherein the DO in the perfusion bioreactor is controlled through adjustment of the rock rate and rock angle of the bioreactor, wherein the bioreactor is initially rocked at 22 rpm with a rock angle of 10° and subsequently rocked at 25 rpm with a rock angle of 12°, and by manually supplying pure oxygen to the headspace when the DO is > 30%, wherein a total gas flow rate is initially 0.2 liters per minute and increased to 0.4 1pm when the cell concentration is ≥ 3 x 10 7 cells/mL or > 4 x 10 7 cells/mL; and wherein the perfusion bioreactor cell culture has a dissolved oxygen concentration of at least about 30%, and wherein the DO in the perfusion bioreactor is controlled through adjustment of the rock rate and rock angle of the bioreactor, wherein the bioreactor is initially rocked at 22 rpm with a rock angle of 10° and subsequently rocked at 25 rpm with a rock angle of 12°, and by manually supplying pure oxygen to the headspace when the DO is > 30%, wherein a total gas flow rate is initially 0.2 liters per minute and increased to 0.4 1pm when the cell concentration is ≥ 3 x 10 7 cells/mL or > 4 x 10 7 cells/mL; and b) adding cryoprotectant to the ultra-high density cell population to produce an ultra-high density frozen cell bank, wherein the ultra-high density frozen cell bank has a concentration of at least about 1.0 x 10 8 cells/mL and a post-thaw viability of at least about 95%, and