Umbilical cord blood (CB) banks usually freeze and store CB for clinical 
transplantation using conventional controlled-rate freezer or the automated 
BioArchive system. The aim of this study is to compare the quality of CB 
cryopreserved with conventional and automated methods and to make clear the 
cause of the quality difference between the two methods. The experiment used 
80 CB units: 40 were conventionally cryopreserved and the remainder were 
cryopreserved with a BioArchive. After thawing, the following measures of CB 
quality were compared: recovery rates of cell count, cell viability of total 
nucleated cells (TNCs), mononuclear cells (MNCs), and CD34+ cells, as well as 
colony-forming unit-granulocyte/macrophage (CFU-GM) content. Additionally, 
processing and storage records were reviewed to quantify the number of exposures 
of CB units at room temperature (transient warming event, TWE), which was 
analyzed in relation to CB quality. MNC and CD34+ cell viability were as 
follows: MNC, 78.2% ± 6.8% (conventional), 81.7% ± 7.2% (automated); CD34+ cell, 
90.6% ± 6.9% (conventional), 94.7% ± 3.5% (automated). The absolute CFU-GM 
content per CB unit was 7.1 × 105 ± 5.9 × 105 with conventional cryopreservation 
and 12.3 × 105 ± 12.0 × 105 with automated cryopreservation. CBs cryopreserved 
with BioArchive showed significantly higher MNC and CD34+ cell viability, and 
CFU-GM content than those conventionally cryopreserved. The CB quality 
comparison depending on the amount of TWEs showed no significant quality 
difference between groups that were more exposed to TWEs and groups that were 
less exposed. CBs cryopreserved with BioArchive were of higher quality than 
conventionally cryopreserved CBs, and the cause of quality difference might be 
due to the difference of freezing conditions rather than the TWE effect.