Human adipose tissue has been shown to contain a population of cells that possesses extensive proliferative capacity and the ability to differentiate into multiple cell lineages. These cells are referred to as adipose tissue-derived stem cells (ADSCs) and are generally similar, though not identical, to mesenchymal stem cells (also referred to as marrow stromal cells). ADSCs for research are most conveniently extracted from tissue removed during an elective cosmetic liposuction procedure but may also be obtained from resected adipose tissue. This chapter describes surgical procedures associated with improved ADSC recovery and the processes by which aspirated adipose tissue is washed and digested with collagenase to yield a heterogeneous population from which ADSCs can be expanded. The large volume of tissue obtained from a liposuction procedure (average approximately 2 L), combined with the relatively high frequency of ADSC within the digestate, yields substantially more stem cells than can be realized from marrow without extensive expansion in culture.