Peripheral adipose tissue contains a population of clonogenic precursor cells referred to as adipose-derived stem cells (ASC) that retain the capacity to differentiate into multiple cell types including osteoblasts, adipocytes, chondrocytes, myocytes, and neuronal cells following ex vivo expansion. Recent studies have demonstrated that ASC are most likely derived from a perivascular niche within highly vascularised fat tissue, analogous to different mesenchymal cell populations identified in other tissues throughout the body. The following chapter describes techniques to prospectively isolate clonogenic ASC from adult human adipose tissue using antibodies directed against perivascular markers and methods to immunophenotypically characterize their ex vivo expanded progeny.