With the emergence of regenerative medicine, many researchers have turned to fat tissue as a source of adipose-derived stem cells (ASCs). Because freshly collected adipose tissue is not always readily available, there will be a need for improved cryopreservation methods to reproducibly maintain ASC viablility and multipotentiality in long-term storage. This study examines the efficiency of conventional dimethyl sulphoxide cryopreservation methods by measuring the maintenance of differentiation potential after one freeze cycle. Additionally, we analysed the viability of ASCs as a function of varying cell concentrations in cryopreservation media. We evaluated four distinct colony-forming unit assays (fibroblast, alkaline phosphatase, adipocyte and osteoblast) to monitor quantitatively the differentiation potential in ASCs after one freeze cycle. We found that the post-thaw viability was a function of storage concentration and that an optimal viability was observed for a concentration of 0.5 x 10(6) cells/ml cryopreservation medium.